Back gate effects on threshold voltage sensitivity to SOI thickness in fully-depleted SOI MOSFETs

The dependence of threshold voltage on silicon-on-insulator (SOI) thickness is studied on fully-depleted SOI MOSFETs, and, for this purpose, back-gate oxide thickness and back gate voltage are varied. When the back gate oxide is thinner than the critical thickness dependent on the back gate voltage, the threshold voltage has a minimum in cases where the SOI film thickness is decreased, because of capacitive coupling between the SOI layer and the back gate. This fact suggests that threshold voltage fluctuations due to SOI thickness variations are reduced by controlling the back gate voltage and thinning the back gate oxide.