Effects of the Gate Offset on Performance of Double-Gate negative Capacitance Field-Effect Transistors

Abstract

Negative capacitance field-effect transistors (NCFETs) have attracted much attention for use in low-power applications, due to subthreshold swing (SS) of sub-60 mV/decade. Recently, there has been increasing interest in the optimization of the NCFETs. For example, it has been reported that the performance of the NCFETs can be enhanced by using the non-uniform thickness of the gate oxide [1] and controlling spacer configurations [2]. As shown in Fig. 1, the source/drain-to-gate offset (Loffset) can also be an important design facto, since the fringing field greatly affects the characteristics of the NCFETs. However, few studies have been done about the effects of the Loffset on the performance. In this work, we investigate the impact of the Loffset on the figure of merits, such as SS, ON-current (ION), and cut-off frequency (fT) of double-gate NCFETs with the gate length of 10 nm. To correctly capture the quantum effects, such as tunneling and confinement in the small scale, the quantum transport simulations in the non-equilibrium Green’s function (NEGF) formalism have been conducted. We have solved 3-D Poisson equation, the NEGF equation, and the multi-domain Landau-Khalatnikov equations self-consistently to model the NC effect. It is found that the ION can be significantly improved by decreasing the Loffset in Fig. 2. However, if taking into account the high frequency applications, the Loffset should be carefully optimized because of the trade-off between the ION and the fT in Fig. 3.