This paper reports recent progress on partially depleted (PD) SOI modeling using a surface potential based approach. The new model, called PSP-SOI, is formulated within the framework of the latest industry standard bulk MOSFET model PSP. In addition to its physics-based formulation and scalability inherited from PSP, PSP-SOI captures SOI specific effects by including a floating body simulation capability, a parasitic bipolar model, and self-heating. A nonlinear body resistance is included for modeling body-contacted SOI devices. The PSP-SOI model has been extensively tested on several PD/SOI technologies.