Analysis of Germanium FinFET logic circuits and SRAMs with asymmetric gate to source/drain underlap devices

Analysis of Germanium FinFET on SOI substrate (GeOI FinFET) at device and circuit level is presented. The amplified Band-To-Band Tunneling (BTBT) leakage of GeOI FinFETs is observed due to the parasitic bipolar effect, and the BTBT induced parasitic bipolar leakage dominates the leakage current of GeOI FinFET. The effectiveness of different dual-Vt technology options including increasing channel doping, increasing gate length and drain-side underlap for leakage reduction is analyzed for GeOI FinFET logic circuits and SRAMs. Drain-side underlap is the most effective way for leakage reduction of GeOI FinFETs, while increasing channel doping is the least effective way for leakage reduction of GeOI FinFETs. An optimum asymmetric underlap design in SRAM using asymmetric underlap pull-up and access transistors (PUAX-asym) is proposed. GeOI FinFETs with asymmetric underlap design show significant improvement in leakage-delay performance and stability in logic circuits and SRAM cells.