This article presents, for the first time, a method to directly calculate the noise parameters (minimum noise figure NFmin, equivalent noise resistance R-n, and optimized source resistance R-opt and reactance X-opt) of metal-oxide-semiconductor field effect transistors based on the HSPICE level 3 model because all the model parameters are available from the manufacturer of our device-under-test. All physically based high frequency noise sources, thermal noise from the channel, gate, source and drain resistances, induced Sate noise, and the correlation among them, are considered. and the impact of gate resistance and induced gate noise on the noise parameters is studied. The method of direct calculation of noise parameters can be applied to any sophisticated small-signal device model.