A surface potential based non-charge-sheet core model for cylindrical undoped surrounding-gate （SRG） MOSFETs is presented. It is based on the exact surface potential solution of Poisson＇s equation and Pao-Sah＇s dual integral without the charge-sheet approximation, allowing the SRG-MOSFET characteristics to be adequately described by a single set of the analytic drain current equation in terms of the surface potential evaluated at the source and drain ends. It is valid for all operation regions and traces the transition from the linear to saturation and from the sub-threshold to strong inversion region without fitting-parameters, and verified by the 3-D numerical simulation.
A semi-empirical analytic model for the threshold voltage instability of a MOSFET is derived from Shockley-Read-Hall （SRH） statistics to account for the transient charging effects in a MOSFET high-k gate stack. Starting from the single energy level and single trap assumption, an analytical expression for the filled trap density in terms of dynamic time is derived from SRH statistics. The semi-empirical analytic model for the threshold voltage instability is developed based on MOSFET device physics between the threshold voltage and the induced trap density. The obtained model is also verified by extensive experimental data of trapping and de-trapping stress from different high-k gate configurations.
A continuous surface potential versus voltage equation is proposed and then its solution is further discussed for a long channel intrinsic surrounding-gate（SRG） MOSFET from the accumulation to strong inversion region.The original equation is derived from the exact solution of a simplified Poisson equation and then the empirical correction is performed from the mathematical condition required by the continuity of the solution,which results in a continuous surface potential versus voltage equation,allowing the surface potential and the related derivatives to be described by an analytic solution from the accumulation to strong inversion region and from linear to the saturation region accurately and continuously.From these results,the dependences of surface potential and centric potential characteristics on device geometry are analyzed and the results are also verified with the 3-D numerical simulation from the aspect of accuracy and continuity tests.
As a connection between the process and the circuit design, the device model is greatly desired for emerging devices, such as the double-gate MOSFET. Time efficiency is one of the most important requirements for device modeling. In this paper, an improvement to the computational efficiency of the drain current model for double-gate MOSFETs is extended, and different calculation methods are compared and discussed. The results show that the calculation speed of the improved model is substantially enhanced. A two-dimensional device simulation is performed to verify the improved model. Furthermore, the model is implemented into the HSPICE circuit simulator in Verilog-A for practical application.
A continuous yet analytic channel potential solution is proposed for doped symmetric double-gate （DG） MOSFETs from the accumulation to the strong-inversion region. Analytical channel potential relationship is derived from the complete 1-D Poisson equation physically, and the channel potential solution of the DG MOSFET is obtained analytically. The extensive comparisons between the presented solution and the numerical simulation illustrate that the solution is not only accurate and continuous in the whole operation regime of DG MOSFETs, but also valid to wide doping concentration and various geometrical sizes, without employing any fitting parameter.
This paper studies an oxide/silicon core/shell nanowire MOSFET （OS-CSNM）. Through three-dimensional device simulations, we have demonstrated that the OS-CSNM has a lower leakage current and higher Ion/Ioff ratio after intro- ducing the oxide core into a traditional nanowire MOSFET （TNM）. The oxide/silicon OS-CSNM structure suppresses threshold voltage roll-off, drain induced barrier lowering and subthreshold swing degradation. Smaller intrinsic device delay is also observed in OS-CSNM in comparison with that of TNM.
A unified charge-based model for fully depleted silicon-on-insulator （SOI） metal oxide semiconductor field-effect transistors （MOSFETs） is presented. The proposed model is accurate and applicable from intrinsic to heavily doped channels with various structure parameters. The framework starts from the one-dimensional Poisson Boltzmann equa- tion, and based on the full depletion approximation, an accurate inversion charge density equation is obtained. With the inversion charge density solution, the unified drain current expression is derived, and a unified terminal charge and intrinsic capacitance model is also derived in the quasi-static case. The validity and accuracy of the presented analytic model is proved by numerical simulations.
