Improved analytical modeling of polysilicon depletion in MOSFETs for circuit simulation

Polysilicon gate depletion is an important effect that degrades the circuit performance of deep submicron standard CMOS technologies. A new approach to analytically modeling the polysilicon depletion effect on drain current and transconductances as well as node charges and transcapacitances is presented. The model is based on a clear physical analysis of the charges in the MOS transistor structure. Using the modeling framework and the fundamental variables of the EKV MOS transistor model formalism and that of the related charges models, a continuous model is achieved that is valid in all operating regions from weak inversion to strong inversion and from nun-saturation to saturation. The asymptotic behavior of the transcapacitances is improved with respect to former model formulations. Only the doping concentration in the polygate is used in addition to the other physical device model parameters. The model shows excellent results in comparison with a surface potential based numerical model and 2D numerical device simulation. The model is efficient for circuit simulation and is further practical for analog circuit design. (C) 2000 Elsevier Science Ltd. All rights reserved.