FinFETs using reverse substrate layer with improved gate capacitance characteristics for subthreshold application

• A novel reverse substrate layer (RSL) is added in conventional FinFET.
• RSL FinFET Cgate roll-off in subthreshold region is exhibited and analyzed.
• RSL FinFETs have higher fT and fmax for subthreshold RF application.

A novel FinFET structure with a reverse substrate layer (RSL FinFET) is proposed to achieve improved gate capacitance characteristics for subthreshold RF application. The inserted reverse substrate layer (RSL) is situated beneath the punch through stop layer (PTSL) with the opposite doping type to PTSL. The RSL FinFETs show reduced gate capacitance (Cg) in subthreshold region at frequencies over 100 Hz. The improved Cg characteristic is attributed to the limitation of carrier transportation from the substrate by implementing the RSL-PTSL junction. Meanwhile, the Id − Vg characteristics are maintained because the RSL only impacts the small-signal AC behavior. Compared to conventional FinFETs, the RSL FinFETs have higher cut-off frequency and maximum frequency of oscillation without any degradation of the device analog performance. Additionally, the fabrication of RSL FinFETs is fully compatible with the state-of-the-art CMOS technology, promising for ultra low power applications.

The RSL FinFETs show reduced gate capacitance (Cg) in subthreshold region at frequencies over 100 Hz. Compared to conventional FinFETs, the RSL FinFETs have higher cut-off frequency and maximum frequency of oscillation without any degradation of the analog performance.Figure optionsDownload as PowerPoint slide