This article presents an extraction method to obtain the channel thermal noise in metal-oxide-semiconductor field effect transistor (MOSFETs) directly from the dc, scattering parameter and rf noise measurements. In this extraction method, the transconductance (gm), output resistance (RDS), and source and drain resistances (RS and RD) are obtained from dc measurements. The gate resistance (RG) is extracted from scattering-parameter measurements, and the equivalent noise resistance (Rn) is obtained from rf noise measurements. This method has been verified by using the measured data of a 0.36 μm n-type MOSFET up to 18 GHz. Comparisons between simulated and measured characteristics of noise parameters versus frequency are also presented.