A process/physics-based compact model (UFDG) for nonclassical MOSFETs having ultra-thin Si bodies (UTB) is overviewed. The model, in essence, is a compact Poisson-Schrodinger solver, including accountings for short-channel effects, and is applicable to nanoscale fully depleted (DG) Sol MOSFETs as well as generic double-gate (DG) devices. The utility of UFDG in nonclassical CMOS device design, as well as circuit design, is stressed, and demonstrated by using it in Spice3 to design UTB MOSFETs and to project extremely scaled DG and FD/SOI CMOS performances. Also, calibration of UFDG to fabricated FinFETs yields new physical insights about these potentially viable nanoscale DG devices, and about model requirements for them. (C) 2004 Elsevier Ltd. All rights reserved.