In this paper, we report the characterization and modeling of multi-finger gate all around (GAA) nanowire (NW) FETs (NWFETs) from dc to 14 GHz. The self-heating effect (SHE) in NWFETs is investigated experimentally using the small-signal output conductance ( g ds\} ) technique. The frequency-dependent complex thermal impedance, Z thf) , is extracted by fitting an n th-order thermal network with the experimental data. We show that the temperature rise Δ T (=85 °C) due to SHE is significant in short-channel silicon on insulator (SOI) NWFETs. Finally, we have evaluated the RF figure of merit (FOM) for these NWFETs as fT (=70 GHz) and f max (=80 GHz). We also report the RF performance metric sensitivity on temperature, partial f max/\textbackslash{}partial T amb ( approx -0.104 GHz/K). The reported BSIM-CMG compact model shows a good correlation with the measurement data.