Device simulation of negative-capacitance field-effect transistors with a uniaxial ferroelectric gate insulator

Abstract

We model the behavior of uniaxial ferroelectrics and simulate planar negative-capacitance (NC) field-effect transistors (FETs) having a gate insulating film made of a uni-axial ferroelectric. The behavior of such NC FETs strongly depends on the direction of the ferroelectric polarization axis. When the direction is away from being parallel to the ferro-electric film to some extent, the ferroelectric polarization becomes larger than the paraelectric polarization and the ferroelectric film begins to act as a negative capacitor. The NC FETs can then be switched on and off more steeply than conventional metal-oxide-semiconductor FETs. This NC effect is maximized at that moment and becomes weaker as the direction approaches perpendicular to the ferroelectric film.