Advanced models for simulation of planar and gate-all-around nanoscale MOSFETs

The aim of this thesis is the development and validation of TCAD tools for both the purpose of device performance analysis and performance improvement. We first present a comparative simulation study of ultra-thin-body strained silicon and III-V semiconductor based MOSFETs by using a comprehensive semiclassical Multisubband Monte Carlo transport model. We then present a new model for the surface roughness scattering. The model is suitable for bulk, for ultra-thin-body and for hetero-structure quantum well MOSFETs. Comparison with experimental mobility for Si bulk MOSFETs shows that a good agreement with measured mobility can be obtained with a r.m.s. value of the surface roughness spectrum close to several AFM and TEM measurements. Finally, we developed a deterministic solver for the Boltzmann transport equation for gate-all-around circular MOSFETs. In particular, we solve the Schrodinger equation for arbitrary crystal transport directions within the effective mass approximation including the wave-function penetration into the oxide and the nonparabolicity of the energy dispersion relation along the quantization plane and transport direction. Then, the BTE is solved without any a-priori assumption and including the main scattering mechanisms responsible for performance degradation, with a new model for the SR scattering