A model based on analysis of the self-consistent Poisson-Schrodinger equation is proposed to investigate the tunneling current of electrons in the inversion layer of a p-type metal-oxide-semiconductor （MOS） structur...A model based on analysis of the self-consistent Poisson-Schrodinger equation is proposed to investigate the tunneling current of electrons in the inversion layer of a p-type metal-oxide-semiconductor （MOS） structure. In this model, the influences of interface trap charge （ITC） at the Si-SiO2 interface and fixed oxide charge （FOC） in the oxide region are taken into account, and one-band effective mass approximation is used. The tunneling probability is obtained by employing the transfer matrix method. Further, the effects of in-plane momentum on the quantization in the electron motion perpendicular to the Si-SiO2 interface of a MOS device are investigated. Theoretical simulation results indicate that both ITC and FOC have great influence on the tunneling current through a MOS structure when their densities are larger than l012 cm 2, which results from the great change of bound electrons near the Si-SiO2 interface and the oxide region. Therefore, for real ultrathin MOS structures with ITC and FOC, this model can give a more accurate description for the tunneling current in the inversion layer.展开更多
Hot carrier injection （HCI） at high temperatures and different values of gate bias Vg has been performed in order to study the actions of negative bias temperature instability （NBTI） and hot carriers. Hot-carrier-...Hot carrier injection （HCI） at high temperatures and different values of gate bias Vg has been performed in order to study the actions of negative bias temperature instability （NBTI） and hot carriers. Hot-carrier-stress-induced damage at Vg = Vd, where Vd is the voltage of the transistor drain, increases as temperature rises, contrary to conventional hot carrier behaviour, which is identified as being related to the NBTI. A comparison between the actions of NBTI and hot carriers at low and high gate voltages shows that the damage behaviours are quite different： the low gate voltage stress results in an increase in transconductance, while the NBTI-dominated high gate voltage and high temperature stress causes a decrease in transconductance. It is concluded that this can be a major source of hot carrier damage at elevated temperatures and high gate voltage stressing of p-channel metal-oxide-semiconductor field-effect transistors （PMOSFETs）. We demonstrate a novel mode of NBTI-enhanced hot carrier degradation in PMOSFETs. A novel method to decouple the actions of NBTI from that of hot carriers is also presented.展开更多
We investigate the impact of random telegraph noise（RTN） on the threshold voltage of multi-level NOR flash memory.It is found that the threshold voltage variation（？Vth） and the distribution due to RTN increase wi...We investigate the impact of random telegraph noise（RTN） on the threshold voltage of multi-level NOR flash memory.It is found that the threshold voltage variation（？Vth） and the distribution due to RTN increase with the programmed level（Vth） of flash cells. The gate voltage dependence of RTN amplitude and the variability of RTN time constants suggest that the large RTN amplitude and distribution at the high program level is attributed to the charge trapping in the tunneling oxide layer induced by the high programming voltages. A three-dimensional TCAD simulation based on a percolation path model further reveals the contribution of those trapped charges to the threshold voltage variation and distribution in flash memory.展开更多
The effects of the oxygen-argon ratio on electric properties of Ta2O5 film prepared by radio-frequency magnetron sputtering were investigated.The Ta2O5 partially transforms from the amorphous phase into the crystal ph...The effects of the oxygen-argon ratio on electric properties of Ta2O5 film prepared by radio-frequency magnetron sputtering were investigated.The Ta2O5 partially transforms from the amorphous phase into the crystal phase when annealing temperatures are 800℃ or higher.The lattice constant of Ta2O5 decreases with the increase of the O2/Ar ratio,which indicates that oxygen gas in the working gas mixture contributes to reducing the density of oxygen vacancies during the deposition process.For the films deposited in working gas mixtures with different O2/Ar ratios and subsequently annealed at 700℃,the effective dielectric constant is increased from 14.7 to 18.4 with the increase of the O2/Ar ratio from 0 to 1.Considering the presence of an SiO2 layer between the film and the silicon substrate,the optimal dielectric constant of Ta2O5 film was estimated to be 31.Oxygen gas in the working gas mixture contributes to reducing the density of oxygen vacancies,and the oxygen vacancy density and leakage current of Ta2O5 film both decrease with the increase of the O2/Ar ratio.The leakage current decreases after annealing treatment and it is minimized at 700℃.However,when the annealing temperature is 800℃ or higher,it increases slightly,which results from the partially crystallized Ta2O5 layer containing defects such as grain boundaries and vacancies.展开更多
The MOSFETs are built on SIMOX material, the chide positive charge, interface state, threshold voltage and leakage current of MOSFETs/SOI after 60Co-rirradiation are measured with I-V technique. The results indicate t...The MOSFETs are built on SIMOX material, the chide positive charge, interface state, threshold voltage and leakage current of MOSFETs/SOI after 60Co-rirradiation are measured with I-V technique. The results indicate that the accumulation rate of chide charge density is more than that of interface state density in dose range of 0-3×104Gy (Si), and the 'on' radiation bias is worst case for NMOSFET and PMOSFET.展开更多
Taking the actual operating condition of complementary metal oxide semiconductor （CMOS） circuit into account, conventional direct current （DC） stress study on negative bias temperature instability （NBTI） neglect...Taking the actual operating condition of complementary metal oxide semiconductor （CMOS） circuit into account, conventional direct current （DC） stress study on negative bias temperature instability （NBTI） neglects the detrapping of oxide positive charges and the recovery of interface states under the ＇low＇ state of p-channel metal oxide semiconductor field effect transistors （MOSFETs） inverter operation. In this paper we have studied the degradation and recovery of NBTI under alternating stress, and presented a possible recovery mechanism. The three stages of recovery mechanism under positive bias are fast recovery, slow recovery and recovery saturation.展开更多
Deep submicron n-channel metal-oxide-semiconductor field-effect transistors （NMOSFETs） with shallow trench isolation （STI） are exposed to ionizing dose radiation under different bias conditions. The total ionizing...Deep submicron n-channel metal-oxide-semiconductor field-effect transistors （NMOSFETs） with shallow trench isolation （STI） are exposed to ionizing dose radiation under different bias conditions. The total ionizing dose radiation induced subthreshold leakage current increase and the hump effect under four different irradiation bias conditions including the worst case （ON bias） for the transistors are discussed. The high electric fields at the corners are partly responsible for the subthreshold hump effect. Charge trapped in the isolation oxide, particularly at the Si/SiO2 interface along the sidewalls of the trench oxide creates a leakage path, which becomes a dominant contributor to the offstate drain-to-source leakage current in the NMOSFET. Non-uniform charge distribution is introduced into a threedimensional （3D） simulation. Good agreement between experimental and simulation results is demonstrated. We find that the electric field distribution along with the STI sidewall is important for the radiation effect under different bias conditions.展开更多
A systematic investigation of γ radiation effects in gate SiO2 as a function of thefluorine ion implantation conditions was performed. It has been found that thegeneration of interface states and oxide trapped charge...A systematic investigation of γ radiation effects in gate SiO2 as a function of thefluorine ion implantation conditions was performed. It has been found that thegeneration of interface states and oxide trapped charges in fluorinated MOSFETsdepends strongly on implantation conditions. The action of F in oxides is theconjunction of positive and negative effects. A model by forming St--F bonds tosubstitute the other strained bonds which easily become charge traps under irradiationand to relax the bond stress on St / SiOZ interface is use'd for experimental explanation.展开更多
Input/output devices for flash memory are exposed to gamma ray irradiation. Total ionizing dose has been shown great influence on characteristic degradation of transistors with different sizes. In this paper, we obser...Input/output devices for flash memory are exposed to gamma ray irradiation. Total ionizing dose has been shown great influence on characteristic degradation of transistors with different sizes. In this paper, we observed a larger increase of off-state leakage in the short channel device than in long one. However, a larger threshold voltage shift is observed for the narrow width device than for the wide one, which is well known as the radiation induced narrow channel effect. The radiation induced charge in the shallow trench isolation oxide influences the electric field of the narrow channel device. Also, the drain bias dependence of the off-state leakage after irradiation is observed, which is called the radiation enhanced drain induced barrier lowing effect. Finally, we found that substrate bias voltage can suppress the off-state leakage, while leading to more obvious hump effect.展开更多
A diagram representation method is proposed to interpret the complicated charge pumping（CP） processes. The fast and slow traps in CP measurement are defined.Some phenomena such as CP pulse rise/fall time dependence,...A diagram representation method is proposed to interpret the complicated charge pumping（CP） processes. The fast and slow traps in CP measurement are defined.Some phenomena such as CP pulse rise/fall time dependence, frequency dependence,the voltage dependence for the fast and slow traps,and the geometric CP component are clearly illustrated at a glance by the diagram representation.For the slow trap CP measurement,there is a transition stage and a steady stage due to the asymmetry of the electron and hole capture,and the CP current is determined by the lower capturing electron or hole component.The method is used to discuss the legitimacy of the newly developed modified charge pumping method.展开更多
The two-dimensional electron gas(2DEG)formed at the interface between two oxide insulators provides new opportunities for electronics and spintronics.The broken inversion symmetry at the heterointerface results in a R...The two-dimensional electron gas(2DEG)formed at the interface between two oxide insulators provides new opportunities for electronics and spintronics.The broken inversion symmetry at the heterointerface results in a Rashba spin-orbit coupling(RSOC)effect that enables the conversion between spin and charge currents.However,conducting oxide interfaces that simultaneously exhibit strong RSOC and high carrier mobility-a combination query for achieving high spin-to-charge inter-conversion efficiencies-remain scarce.Herein,we report a correlated 2DEG with giant Rashba splitting and high electron mobility in(111)-oriented EuTiO_(3)/KTaO_(3)(ETO/KTO)heterostructures under light illumination.Upon light modulation,a unique carrier-dependent giant anomalous Hall effect,the signature of spin-polarized 2DEG,emerges with a sign crossover at a carrier density of approximately 5.0×10^(13)cm^(-2),highlighting dramatic changes in the band topology of KTO(111)interface.Furthermore,at 2 K,the carrier mobility is enhanced from 103 cm^(2)·V^(-1)·s^(-1)to 1800 cm^(2)·V^(-1)·s^(-1),a remarkable enhancement of approximately 20 times.Accompanying with a giant Rashba coefficient αR up to 360meV·˚A,this high mobility ferromagnetic 5d oxide 2DEG is predicted to achieve a giant spin-to-charge conversion efficiency ofλ~10 nm,showing great potential for designing low-power spin-orbitronic devices.展开更多
An improved hot carrier injection （HCI） degradation model was proposed based on interface trap generation and oxide charge injection theory. It was evident that the degradation behavior of electric parameters such a...An improved hot carrier injection （HCI） degradation model was proposed based on interface trap generation and oxide charge injection theory. It was evident that the degradation behavior of electric parameters such as Idlin, Idsat, Gm and Vt fitted well with this model. Devices were prepared with 0.35μm technology and different LDD processes. Idlin and Idsat after HCI stress were analyzed with the improved model. The effects of interface trap generation and oxide charge injection on device degradation were extracted, and the charge injection site could be obtained by this method. The work provides important information to device designers and process engineers.展开更多
In this paper, total ionizing dose effect of NMOS transistors in advanced CMOS technology are exam- ined. The radiation tests are performed at 60Co sources at the dose rate of 50 rad （Si）/s. The investigation＇s res...In this paper, total ionizing dose effect of NMOS transistors in advanced CMOS technology are exam- ined. The radiation tests are performed at 60Co sources at the dose rate of 50 rad （Si）/s. The investigation＇s results show that the radiation-induced charge buildup in the gate oxide can be ignored, and the field oxide isolation struc- ture is the main total dose problem. The total ionizing dose （TID） radiation effects of field oxide parasitic transistors are studied in detail. An analytical model of radiation defect charge induced by TID damage in field oxide is estab- lished. The I-V characteristics of the NMOS parasitic transistors at different doses are modeled by using a surface potential method. The modeling method is verified by the experimental I V characteristics of 180 nm commer- cial NMOS device induced by TID radiation at different doses. The model results are in good agreement with the radiation experimental results, which shows the analytical model can accurately predict the radiation response characteristics of advanced bulk CMOS technology device.展开更多
The effects of gamma irradiation on the shallow trench isolation（STI）leakage currents in a 0.18μm technology are investigated.NMOSFETs with different gate lengths are irradiated at several dose levels.The threshold...The effects of gamma irradiation on the shallow trench isolation（STI）leakage currents in a 0.18μm technology are investigated.NMOSFETs with different gate lengths are irradiated at several dose levels.The threshold voltage shift is negligible in all of the devices due to the very thin oxide thickness.However,an increase in the off-state leakage current is observed for all of the devices.We believe that the leakage is induced by the drain-to-source leakage path along the STI sidewall,which is formed by the positive trapped charge in the STI oxide.Also, we found that the leakage is dependent on the device＇s gate length.The three-transistor model（one main transistor with two parasitic transistors）can provide us with a brief understanding of the dependence on gate length.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 61076055)the Program for Innovative Research Team of Zhejiang Normal University of China (Grant No. 2007XCXTD-5)the Open Program of Surface Physics Laboratory of Fudan University, China (Grant No. FDSKL2011-04)
文摘A model based on analysis of the self-consistent Poisson-Schrodinger equation is proposed to investigate the tunneling current of electrons in the inversion layer of a p-type metal-oxide-semiconductor （MOS） structure. In this model, the influences of interface trap charge （ITC） at the Si-SiO2 interface and fixed oxide charge （FOC） in the oxide region are taken into account, and one-band effective mass approximation is used. The tunneling probability is obtained by employing the transfer matrix method. Further, the effects of in-plane momentum on the quantization in the electron motion perpendicular to the Si-SiO2 interface of a MOS device are investigated. Theoretical simulation results indicate that both ITC and FOC have great influence on the tunneling current through a MOS structure when their densities are larger than l012 cm 2, which results from the great change of bound electrons near the Si-SiO2 interface and the oxide region. Therefore, for real ultrathin MOS structures with ITC and FOC, this model can give a more accurate description for the tunneling current in the inversion layer.
基金Project supported by the National Natural Science Foundation of China （Grant No 60206006）. the Program for New Century Excellent Talents of Ministry of Education of China （Grant No 681231366）. the National Defense Pre-Research Foundation of China （Grant No 51408010305DZ0168） and the Key Project of Chinese Ministry of Education （Grant No 104172）.
文摘Hot carrier injection （HCI） at high temperatures and different values of gate bias Vg has been performed in order to study the actions of negative bias temperature instability （NBTI） and hot carriers. Hot-carrier-stress-induced damage at Vg = Vd, where Vd is the voltage of the transistor drain, increases as temperature rises, contrary to conventional hot carrier behaviour, which is identified as being related to the NBTI. A comparison between the actions of NBTI and hot carriers at low and high gate voltages shows that the damage behaviours are quite different： the low gate voltage stress results in an increase in transconductance, while the NBTI-dominated high gate voltage and high temperature stress causes a decrease in transconductance. It is concluded that this can be a major source of hot carrier damage at elevated temperatures and high gate voltage stressing of p-channel metal-oxide-semiconductor field-effect transistors （PMOSFETs）. We demonstrate a novel mode of NBTI-enhanced hot carrier degradation in PMOSFETs. A novel method to decouple the actions of NBTI from that of hot carriers is also presented.
基金supported by the National Research Program of China(Grant No.2016YFB0400402)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20141321)the National Natural Science Foundation of China(Grant No.61627804)
文摘We investigate the impact of random telegraph noise（RTN） on the threshold voltage of multi-level NOR flash memory.It is found that the threshold voltage variation（？Vth） and the distribution due to RTN increase with the programmed level（Vth） of flash cells. The gate voltage dependence of RTN amplitude and the variability of RTN time constants suggest that the large RTN amplitude and distribution at the high program level is attributed to the charge trapping in the tunneling oxide layer induced by the high programming voltages. A three-dimensional TCAD simulation based on a percolation path model further reveals the contribution of those trapped charges to the threshold voltage variation and distribution in flash memory.
基金Project supported by the National Natural Science Foundation of China (Grant No. 61076055)the Program for Innovative Research Teams in Zhejiang Normal Universitythe Open Project Program of Surface Physics Laboratory (National Key Laboratory) of Fudan University (Grant No. FDS KL2011_04)
文摘The effects of the oxygen-argon ratio on electric properties of Ta2O5 film prepared by radio-frequency magnetron sputtering were investigated.The Ta2O5 partially transforms from the amorphous phase into the crystal phase when annealing temperatures are 800℃ or higher.The lattice constant of Ta2O5 decreases with the increase of the O2/Ar ratio,which indicates that oxygen gas in the working gas mixture contributes to reducing the density of oxygen vacancies during the deposition process.For the films deposited in working gas mixtures with different O2/Ar ratios and subsequently annealed at 700℃,the effective dielectric constant is increased from 14.7 to 18.4 with the increase of the O2/Ar ratio from 0 to 1.Considering the presence of an SiO2 layer between the film and the silicon substrate,the optimal dielectric constant of Ta2O5 film was estimated to be 31.Oxygen gas in the working gas mixture contributes to reducing the density of oxygen vacancies,and the oxygen vacancy density and leakage current of Ta2O5 film both decrease with the increase of the O2/Ar ratio.The leakage current decreases after annealing treatment and it is minimized at 700℃.However,when the annealing temperature is 800℃ or higher,it increases slightly,which results from the partially crystallized Ta2O5 layer containing defects such as grain boundaries and vacancies.
文摘The MOSFETs are built on SIMOX material, the chide positive charge, interface state, threshold voltage and leakage current of MOSFETs/SOI after 60Co-rirradiation are measured with I-V technique. The results indicate that the accumulation rate of chide charge density is more than that of interface state density in dose range of 0-3×104Gy (Si), and the 'on' radiation bias is worst case for NMOSFET and PMOSFET.
基金Project supported by the National Natural Science Foundation of China （Grant No 60376024） and the National High Technology Research and Development Program of China （Grant No 2003AA1Z1630）. The authors thank SMIC for the supply of test devices.
文摘Taking the actual operating condition of complementary metal oxide semiconductor （CMOS） circuit into account, conventional direct current （DC） stress study on negative bias temperature instability （NBTI） neglects the detrapping of oxide positive charges and the recovery of interface states under the ＇low＇ state of p-channel metal oxide semiconductor field effect transistors （MOSFETs） inverter operation. In this paper we have studied the degradation and recovery of NBTI under alternating stress, and presented a possible recovery mechanism. The three stages of recovery mechanism under positive bias are fast recovery, slow recovery and recovery saturation.
文摘Deep submicron n-channel metal-oxide-semiconductor field-effect transistors （NMOSFETs） with shallow trench isolation （STI） are exposed to ionizing dose radiation under different bias conditions. The total ionizing dose radiation induced subthreshold leakage current increase and the hump effect under four different irradiation bias conditions including the worst case （ON bias） for the transistors are discussed. The high electric fields at the corners are partly responsible for the subthreshold hump effect. Charge trapped in the isolation oxide, particularly at the Si/SiO2 interface along the sidewalls of the trench oxide creates a leakage path, which becomes a dominant contributor to the offstate drain-to-source leakage current in the NMOSFET. Non-uniform charge distribution is introduced into a threedimensional （3D） simulation. Good agreement between experimental and simulation results is demonstrated. We find that the electric field distribution along with the STI sidewall is important for the radiation effect under different bias conditions.
文摘A systematic investigation of γ radiation effects in gate SiO2 as a function of thefluorine ion implantation conditions was performed. It has been found that thegeneration of interface states and oxide trapped charges in fluorinated MOSFETsdepends strongly on implantation conditions. The action of F in oxides is theconjunction of positive and negative effects. A model by forming St--F bonds tosubstitute the other strained bonds which easily become charge traps under irradiationand to relax the bond stress on St / SiOZ interface is use'd for experimental explanation.
文摘Input/output devices for flash memory are exposed to gamma ray irradiation. Total ionizing dose has been shown great influence on characteristic degradation of transistors with different sizes. In this paper, we observed a larger increase of off-state leakage in the short channel device than in long one. However, a larger threshold voltage shift is observed for the narrow width device than for the wide one, which is well known as the radiation induced narrow channel effect. The radiation induced charge in the shallow trench isolation oxide influences the electric field of the narrow channel device. Also, the drain bias dependence of the off-state leakage after irradiation is observed, which is called the radiation enhanced drain induced barrier lowing effect. Finally, we found that substrate bias voltage can suppress the off-state leakage, while leading to more obvious hump effect.
基金Project supported by the Micro/Nano-Electronics Science and Technology Innovation Platform of Fudan University,National Natural Science Foundation of China(No.60936005)the National VLSI Project(No.2009ZX02035-003).
文摘A diagram representation method is proposed to interpret the complicated charge pumping（CP） processes. The fast and slow traps in CP measurement are defined.Some phenomena such as CP pulse rise/fall time dependence, frequency dependence,the voltage dependence for the fast and slow traps,and the geometric CP component are clearly illustrated at a glance by the diagram representation.For the slow trap CP measurement,there is a transition stage and a steady stage due to the asymmetry of the electron and hole capture,and the CP current is determined by the lower capturing electron or hole component.The method is used to discuss the legitimacy of the newly developed modified charge pumping method.
基金supported by the Science Center of the National Science Foundation of China(Grant No.52088101)the National Key Research and Development Program of China(Grant Nos.2023YFA1406400,2021YFA1400300,and 2023YFA1607403)the National Natural Science Foundation of China(Grant Nos.T2394472 and T2394470).
文摘The two-dimensional electron gas(2DEG)formed at the interface between two oxide insulators provides new opportunities for electronics and spintronics.The broken inversion symmetry at the heterointerface results in a Rashba spin-orbit coupling(RSOC)effect that enables the conversion between spin and charge currents.However,conducting oxide interfaces that simultaneously exhibit strong RSOC and high carrier mobility-a combination query for achieving high spin-to-charge inter-conversion efficiencies-remain scarce.Herein,we report a correlated 2DEG with giant Rashba splitting and high electron mobility in(111)-oriented EuTiO_(3)/KTaO_(3)(ETO/KTO)heterostructures under light illumination.Upon light modulation,a unique carrier-dependent giant anomalous Hall effect,the signature of spin-polarized 2DEG,emerges with a sign crossover at a carrier density of approximately 5.0×10^(13)cm^(-2),highlighting dramatic changes in the band topology of KTO(111)interface.Furthermore,at 2 K,the carrier mobility is enhanced from 103 cm^(2)·V^(-1)·s^(-1)to 1800 cm^(2)·V^(-1)·s^(-1),a remarkable enhancement of approximately 20 times.Accompanying with a giant Rashba coefficient αR up to 360meV·˚A,this high mobility ferromagnetic 5d oxide 2DEG is predicted to achieve a giant spin-to-charge conversion efficiency ofλ~10 nm,showing great potential for designing low-power spin-orbitronic devices.
基金supported by the Shanghai Rising-Star Program(No.07QB14018)
文摘An improved hot carrier injection （HCI） degradation model was proposed based on interface trap generation and oxide charge injection theory. It was evident that the degradation behavior of electric parameters such as Idlin, Idsat, Gm and Vt fitted well with this model. Devices were prepared with 0.35μm technology and different LDD processes. Idlin and Idsat after HCI stress were analyzed with the improved model. The effects of interface trap generation and oxide charge injection on device degradation were extracted, and the charge injection site could be obtained by this method. The work provides important information to device designers and process engineers.
基金Project supported by the National Natural Science Foundation of China(No.11305126)
文摘In this paper, total ionizing dose effect of NMOS transistors in advanced CMOS technology are exam- ined. The radiation tests are performed at 60Co sources at the dose rate of 50 rad （Si）/s. The investigation＇s results show that the radiation-induced charge buildup in the gate oxide can be ignored, and the field oxide isolation struc- ture is the main total dose problem. The total ionizing dose （TID） radiation effects of field oxide parasitic transistors are studied in detail. An analytical model of radiation defect charge induced by TID damage in field oxide is estab- lished. The I-V characteristics of the NMOS parasitic transistors at different doses are modeled by using a surface potential method. The modeling method is verified by the experimental I V characteristics of 180 nm commer- cial NMOS device induced by TID radiation at different doses. The model results are in good agreement with the radiation experimental results, which shows the analytical model can accurately predict the radiation response characteristics of advanced bulk CMOS technology device.
文摘The effects of gamma irradiation on the shallow trench isolation（STI）leakage currents in a 0.18μm technology are investigated.NMOSFETs with different gate lengths are irradiated at several dose levels.The threshold voltage shift is negligible in all of the devices due to the very thin oxide thickness.However,an increase in the off-state leakage current is observed for all of the devices.We believe that the leakage is induced by the drain-to-source leakage path along the STI sidewall,which is formed by the positive trapped charge in the STI oxide.Also, we found that the leakage is dependent on the device＇s gate length.The three-transistor model（one main transistor with two parasitic transistors）can provide us with a brief understanding of the dependence on gate length.
