A static, physical VDMOS model based on the charge-sheet model

A physically based VDMOS model is derived based on the charge-sheet analysis. This is the first time a charge-sheet approach has been successfully used to model VDMOS. The continuous nature of the charge-sheet model results in a continuous I-V model for VDMOS from subthreshold to saturation. The generalized form of the charge-sheet model enables the physical modeling of the nonuniform doping through the MOS channel region of the VDMOS. A physical model of the drift region is combined with the channel model to give a complete physical system of equations which is solved numerically. The model includes detailed calculations of the drift region parameters including the variation of the internal depletion widths with external bias. The physical, continuous behavior of the model provides easy extraction of small signal parameters and interelectrode capacitances. PISCES simulations are used extensively during the development to provide physical insight into the device behavior. Test measurements of VDMOS are used to verify the model.