Process design for integrated circuit manufacturing has traditionally been implemented with little simulation prior to fabrication. As with circuit design of a decade ago, the available simulation tools were mainframe-based, often incompatible, and lacked accurate physical models. Recent developments in process and device simulation allow accurate process modeling which reflect actual fabrication plant capabilities. A highly structured simulation environment implemented for development of Texas Instruments' PRISM\spTM technology is described, together with results of a simulation approach to circuit model development for a new class of silicon power transistors. A new analytical model for field effect transistor modeling is also proposed. This new model preserves continuity of both the drain current and conductance over all bias conditions. It also accurately models the effects of substrate bias on device behavior.