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 (C-g) in subthreshold region at frequencies over 100 Hz. The improved C-g characteristic is attributed to the limitation of carrier transportation from the substrate by implementing the RSL-PTSL junction. Meanwhile, the I-d-V-g 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. (C) 2014 Elsevier Ltd. All rights reserved.