Subthreshold Behavior of Undoped DG MOSFETs

Undoped-body MOSFETs display peculiar semiconductor body thickness dependent subthreshold regions. The very concept of threshold voltage in undoped-body devices is affected by the interpretation given to this behavior. The fundamental subthreshold behavior is examined here from the point of view of its extension and slope factor. Its dependence on technological parameters is analyzed in light of phenomenological considerations. It is found that the subthreshold region may potentially exhibit two coexisting subregions with ideal slope factors of 60 and 120 mV/dec.