MOS device technology is undergoing a constant shrinking process. According to the International Technology Roadmap for Semiconductor Devices 2003, the printed gate length will scale down to 28 nm by 2009. Fully-depleted devices such as FinFETs emerged as promising candidates to replace bulk MOS field-effect transistors due to their immunity against short-channel effects. FinFET devices with a gate width of only 6.5 nm have already been reported. In contrast to bulk MOSFETs, these devices inherently require three-dimensional investigations. Unfortunately, with shrinking device dimensions classical device simulation becomes more and more inaccurate. A rigorous Schrödinger-Poisson solver would be necessary to accurately describe the device behavior. As such simulations are computationally extremely demanding, due to the large number of grid points in three-dimensional problems, they are normally not appropriate. Instead, classical device simulations with additional quantum correction models can be used.

The drift-diffusion model estimates an exponential increase of the carrier concentration towards the Si/SiO₂ interface. Quantum mechanical simulations show, however, that the charge centroid is located several angstroms away from the interface. Therefore, several quantum confinement models have been proposed.

The density-of-states (DOS) correction reduces the DOS at the Si/SiO₂ interface, which is classically modeled as a constant value throughout homogenous materials. Therefore, the carrier concentration at the interface is reduced. An alternative approach is based on the first eigenvalue of the triangular energy well at the interface. The band edge of the conduction band at the interface is set to this eigenvalue and therefore increases the bandgap.

The figure shows the carrier concentration within the fin of a FinFET structure. The simulations have been performed with classical drift-diffusion simulation and the band edge correction model, respectively.