A Unified Continuous and Discrete Model for Double-Gate MOSFETs With Spatially Varying or Pulsed Doping Profiles

This paper presents a unified continuous and discrete model covering all device operating regions of double-gate MOSFETs for the first time. With a specific variable transformation method, the 1-D Poisson's equation in the Cartesian coordinate for double-gate MOSFETs is transformed into the corresponding form in the cylindrical coordinate. Such a transformed cylindrical Poisson's equation results in a simple algebraic equation, which correlates the (inversion-charge induced) surface potential to the field and allows the long-channel drain-current formula to be derived from the Pao-Sah integral. This model can be readily applied to predict the effects of both continuous and discrete doping variations. The short-channel-effect model is also developed by solving the 2-D Poisson's equation using the eigenfunction-expansion method. The accuracy of both long-channel and short-channel models is confirmed by the numerical calculations and TCAD simulations.