L-shaped tunnel FET with stacked gates to suppress the corner effect

An L-shaped tunnel FET (TFET) has strong advantages over a conventional planar TFET, since it can achieve a higher ON-state current and lower subthreshold swing (S) without any integration density loss. However, it suffers from hump behavior in the transfer curve, which is attributed to the electric field crowding effect at the sharp source corner. In this paper, we propose a structural solution without additional thermal processing. Based on the L-shaped TFET, a stacked-gate structure is applied to reduce the electric field crowding effect at the sharp source corner by adopting a high work function (WF) locally. Furthermore, using simulation of the band-to-band tunneling generation, the relationship between the stacked gate and ambipolar current (I-AMB) is analyzed. Then, the stacked gate is modified to meet the low S requirement and reduce I-AMB by using a high-WF gate at the corner. Finally, we present the fabrication method for an L-shaped TFET with stacked gate using a sidewall spacer technique. (c) 2019 The Japan Society of Applied Physics