A physical model and a computer simulation program for nanoscale ballistic SOI MOSFETs are developed. The model includes transistor parameters such as the type and level of doping in the source and drain regions, gate length, Si and gate-oxide thicknesses, spacer length, gate-material work function, etc. Transistor performance is characterized in terms of transconductance, subthreshold slope, on- and off-state drain currents, gate–source overlap capacitance, etc. The software enables one to optimize the transistor parameters.