In this paper, we present a physics-based gate current model for submicron n-type fully depleted SOI MOSFETs. The gate current model is developed by using the conventional lucky-electron concept and quantum-mechanical tunneling mechanism, and the effect of self-heating of SOI device is included. First, the channel electric field is calculated, and then the electron temperature is generated; the electron temperature is derived using a simplified energy balance equation. From the electron temperature, we can calculate the non-local gate current. This model is a time-saving CAD model and many interesting and important device physics about gate current can be found. The accuracy of the presented model has been verified with the experimental data of SOI devices.