Simulation and analysis of the frequency performance of a new silicon nanowire MOSFET structure

Abstract

In this work we used a three-dimensional quantum mechanical simulation approach to simulate a silicon nanowire MOSFET with square cross section. Different gate structures such as double-gate and gate-all-around with a square gate around the wire (square gate-all-around) and with an octagonal gate around the wire (octagonal gate-all-around) are investigated. The Poisson and the Schrödinger equations are solved self-consistently in this analysis. For solving the Poisson equation the Newton–Raphson method and for solving the Schrödinger equation the non-equilibrium Green's function approach are used. By this simulator the drain current and the electron density and their variations versus the gate voltage are obtained. The transconductance (gm), the gate capacitance (CG) and then the cut-off frequency (fT) are calculated. The short channel effects (i.e. the subthreshold slope and the drain off-current) versus variation of the silicon thickness are obtained. We compared gm, CG and fT for different structures of silicon nanowire MOSFET, i.e. the double-gate, the square gate-all-around and the octagonal gate-all-around due to variation of the gate voltage, the oxide thickness and the silicon thickness. Some advantages for the proposed gate-all-around structure over the other structures are observed.