The introduction of n– regions makes an LDD MOSFET behave differently from a conventional MOSFET. The source-and-drain series resistance, which consists of the n+-and-n–regions, shows a strong dependence on the gate bias. Also, the apparent effective length can vary with gate bias. These special features cause the traditional method to determine effective channel length and series resistance inapplicable. In this letter, we propose a method to determine the “intrinsic” channel length and gate-voltage-dependent source-and-drain series resistance of an LDD MOSFET and a model for the LDD device current at small drain-source voltage.