An improved small-signal model for nanometer metal-oxide-semiconductor field-effect transistor (MOSFET) device is presented in this paper. The skin effect and multiple-cell effect are both taken into account. In the extracting procedure, the parameters of elementary cells are determined from the conventional model based on the scalable rules. This small-signal model was validated by the good agreement between measured and simulated S-parameters of 8×0.6×12 μm (number of gate fingers×unit gatewidth×cells) 90-nm gatelength MOSFET under three bias points up to 40 GHz.