Channel electron and hole mobilities in MOSFETs have been extracted in terms of the effective vertical field for several substrate biases. After ascertaining that the 2-D drift–diffusion numerical device simulator is reproducing the substrate charge variation in the MOSFET with respect to the gate voltage, obtained from C–V data, the mobility versus effective field behavior is extracted by comparing the simulated and measured Id–Vgs characteristics. A simple model has been constructed to fit the extracted mobility data in weak and strong inversion, for inversion-layer electrons and holes in n-MOSFET and p-MOSFET, respectively.