This paper describes the direct current characteristics of various silicon-on-insulator (SOI) insulated-gate p-n junction devices, and also proposes equivalent circuit models to permit circuit simulations. Fundamental device models are investigated using a device simulator. It is clarified that device characteristics can be explained on the basis of p-n junction, n-MOSFET, and p-MOSFET (MOSFET, metal-oxide-semiconductor field-effect-transistor) operations. The proposed equivalent circuit models of the devices utilize standard simulation with integrated circuit emphasis circuit elements. Equivalent circuit models can be applied to evaluate the performance of various circuits. (C) 2003 The Electrochemical Society.