In this paper, a unified analytical l-V model for silicon-on-insulator (SOI) MOSFET is presented. The model is valid for possible transitions between partially depleted and fully depleted modes during the transistor operation. It is based on a non-pinned surface potential approach that is valid for all regions of operation. Small geometry effects such as channel length modulation and high field mobility effects are also included. It also considers the self-heating effect, which is important for complete modeling of SOI devices. To include the floating body effect, the parasitic current in each mode of operation is modeled with a proper formulation while a smoothing function is invoked for the transition between the operation modes. A comparison between the model and the experimental results shows good agreement over a wide range of drain and gate voltages. (C) 2003 Elsevier Ltd. All rights reserved.