This paper presents a non-quasi-static (NQS) thermal noise model of the MOS transistor that is valid in all modes of operation, from weak to strong inversion, and up to frequencies which are near or above the NQS cut-off frequency. It is shown that in addition to the well-known induced gate noise (IGN) there is also an induced substrate noise that is generated and that the source and drain noises are also affected. All prior publications on the subject only deal with IGN in strong inversion regime. It is shown that significant differences are obtained for moderate and weak inversion operation. The paper starts with a brief review of NQS model valid in all modes of operation. It then presents a general thermal noise model using four noisy current sources. The power spectral and cross power spectral densities of these noise sources are computed. A first-order approximation is then derived and compared to the complete model. Noise excess factors for the drain and the gate noise are then calculated and the correlation coefficient between the drain and the gate noise is obtained. It is shown that this correlation factor is always null in conduction (VD = VS), and varies in saturation between j0.6 in weak inversion to j0.4 in strong inversion. To our knowledge, it is the first time that a complete HF thermal noise model of the MOST is presented, that is valid in all modes of inversion and up to and above the NQS cut-off frequency.