Floating effective back-gate effect on the small-signal output conductance of SOI MOSFETs

This paper investigates the influence of the silicon substrate. on the ac characteristics of silicon-on-insulator (SOI) MOSFETs. It is shown for the first time that the presence of the substrate, underneath the buried oxide results in two transitions (i.e., zero-pole doublets) in the frequency response of the output conductance. It is demonstrated that the appearance of these transitions, the position and-amplitude of which strongly depend on the substrate doping, is caused by the variation of the potential at substrate-buried oxide interface, which we call the Floating Effective Back-Gate (FEBG) effect. A first-order small-signal equivalent circuit is proposed to. support our observations