Closed-form expressions for the gate-leakage resistance; Rp and its associated noise temperature; Tp; are presented. Tp represents the noise contribution caused by the gate-current Ig. Both Rp and Tp are expressed as functions of the measured noise parameters Rn; Fmin and Zopt. We present both frequency independent expressions and frequency dependent equations and discuss their accuracy. Unique relationships between the measured noise parameters are discussed in addition to the effect on measurement accuracy; careful de-embedding and physical relevance of the model used. Based on this extended threetemperature noise model ; we show by measurements on HEMTs and 90 nm CMOS transistors; that we can model Rn; Fmin and Zopt very accurately at least up to 26 GHz. In addition; the CMOS model has been verified by S-parameters up to 62.5 GHz.