We present an accurate non-quasi-static small-signal MOSFET model incorporating distributed channel and substrate resistances to extend the frequency limit of the model validity to higher frequencies. The model parameters are accurately determined using a new semi-analytical extraction technique combining analytical and optimization approaches as an effective way to attain a global minimum. The validity of the model and parameter extraction method is justified by observing excellent agreements between the measured and modeled S-parameters in the wide range of frequency.