Physical and CAD models for the implanted-channel VLSI MOSFET

A new approach is described for the modeling of practical MOS transistors that have nonuniform substrate doping profiles. The threshold characteristic is used to provide an accurate measure of body charge and thereby to give operating point dependences of the threshold voltage, body effect, mobility, and weak-inversion conduction. The results are incorporated into a simple and flexible CAD model suitable for existing and foreseeable devices. The model has continuity of current and all derivatives throughout all regions of operation. It provides an accurate representation of real transistors and minimizes numerical problems of convergence and stability. It has been implemented as level-4 in SPICE 2G.5 and is freely available for VLSI circuit design.