This work details the harmful effect of parasitic resistances and capacitances on RF figures of merit (FoM) of ultra-thin body and thin buried oxide (UTBB) FD SOI n-MOSFETs. It is demonstrated that intrinsically, UTBB device can reach very high cut-off frequency (f(T)) provided the reduction of parasitic elements. In addition, based on device simulation, we demonstrate that with appropriate configuration, Asymmetric Double Gate (ADG) regime provides a slight improvement of RF figures-of-merit. (C) 2014 Elsevier Ltd. All rights reserved.