A Novel U-Shaped Finfet with Vertical Channels

A novel U-shaped FinFET (UFET) with vertical channels is introduced in this work. A main feature of this device is that it consists of two fins with vertical channels. A top portion of one fin serves as the transistor source, and the top portion of another fin serves as the drain. Unlike traditional FinFETs, gate length (L_g) of the UFET depends on the fin height, whereas gate width (W_g) depends on the fin length. With vertical channels, device footprint scaling would not necessarily need to reduce the gate length. The source and drain is on the same plane and naturally isolated from each other which help to reduce the coupling between them in the subthreshold region. Therefore, the UFET structure has excellent short channel effect (SCE) control, and its effective gate width is significantly increased when compared to traditional FinFETs at the same device footprint, thus considerably increasing drive current and achieving low leakage current at the same time. TCAD simulation of an n-type UFET with L_g = 30 nm shows that the device drive current can achieve 3.46 mA/um at 26 nA/um I_off and 0.75V. An outstanding subthreshold slope (S.S.) of 64 mV/dec. and 9 mV/V DIBL are achieved. A 78% effective gate width increase is achieved when compared with conventional logic FinFETs at the same device footprint. Moreover, 3D NOR flash can be easily built by this UFET.