A methodology combining a thermal-circuit model and device simulation is presented for SOI device simulation including self-heating. The efficiency and accuracy were verified against the rigorous device simulation based on energy balance, Poison, and heat flow equations. In addition, a simple thermal circuit is proposed to model temperature variation in the SOI silicon film. The temperature distribution in the silicon film obtained from the proposed thermal-circuit model is in good agreement with the rigorous device simulation. In high driving current situations, temperature variation in the SOI silicon film is considerably large. Such a model will provide more useful information than the existing constant-temperature model. (C) 2002 Elsevier Science Ltd. All rights reserved.