Abstract A novel subthreshold swing model that linearly depends on the drain bias voltage (Vds) and negative-exponentially depends on the effective channel length (Leff) is proposed for LDD MOSFETs on 90 nm CMOS technology. It simplifies the description of the effective gate overdrive voltage (Vgte) and yields a single-equation I–V compact model to present the transition of the drain current (Ids) between subthreshold and strong inversion. The simulation shows an excellent prediction to the characteristics of sub-100 nm MOSFETs especially in the subthreshold region that is very important in reliability analysis of short channel devices. Compared with the existing threshold voltage-based compact models, the modeling is low in calculation consumptions therefore suitable for the circuit simulation.