New MOSFET architectures are presently being developed in which dielectrics with high permittivity are introduced to replace SiO2-based dielectrics, which are at the end of the scaling roadmap, and where also metal gates are used to replace poly-Si gate to avoid poly-depletion effects. Key in the success of this development is the electrical behavior of such high k/metal gate devices, and more specifically the Bias-Temperature- Instabilities, which are well-known reliability problems in MOS gate stacks. In this thesis, these Bias-Temperature effects will be investigated: the electrical...