Analytic Oxide Capacitance Model of Double- and Surrounding-Gate Metal–Oxide–Semiconductor Field-Effect Transistors in Linear Region by Considering Inversion-Layer Capacitance

Abstract

Inversion charge (Qi) and oxide capacitance (Cox') of undoped (or lightly doped) or doped double-gate (DG) and surrounding-gate (SG) metal–oxide–semiconductor field-effect transistors (MOSFETs) with long channel were analytically modeled by considering inversion-layer capacitance (Ci) in linear region. The Qi model of DG and SG MOSFETs was derived with a closed-form as a function of gate bias (VGS), threshold voltage (Vth), and body structure factor (n) using one-dimensional (1D) Poisson's equation considering the mobile carrier. The n which reflects silicon body structure effect is 1 for DG MOSFETs and less than 1 for SG MOSFETs irrespective of channel doping (Nb). From the derived Qi model considering the Ci effect, the Cox' was modeled and applied to the ID–VGS model of undoped or doped DG and SG MOSFETs in linear region. The compact current model using our proposed Cox' predicted more accurately the on-current behavior than that with the oxide capacitance (Cox) in linear region.