The downscaling of CMOS processes has led to devices with an impressive RF performance. Advanced nanoscale RF MOSFETs present very high transit frequency, which can be traded off with lower power consumption, by shifting the operating point towards the weak inversion (WI) regime. This paper explores whether the simple RF schematics and models used in strong inversion remain valid in moderate or even down to deep WI regions for nanoscale devices. A simple RF equivalent circuit is proposed, leading to first-order analytical expressions, which are able to describe the RF small-signal behavior of nanoscale MOSFET, including noise, across all inversion levels. Using these expressions it is possible to extract the values of all the RF components and noise model parameters directly from measurements. The analytical models are compared to RF measurements of a commercial state-of-the-art 40-nm CMOS process and to the advanced BSIM6 compact bulk MOSFET model, showing very good accuracy.