Negative Bias Temperature Instability (NBTI) continuously ranks amongst the most serious reliability challenges in the development of present-day semiconductor devices. A recently proposed mechanism involving interface state generation triggered by charge trapping appears to be the most promising explanation to this still strongly disputed issue. Charge trapping is assumed to proceed via Lattice Relaxation Multiphonon Emission (LRME), already well-known in the context of random telegraph noise. Within this model, the joint system consisting of the electron energy and the trap energy has to surmount a certain energy barrier. The height of this barrier is related to the time required for the charge trapping event to occur. This time can be accelerated by elevated temperatures according to an Arrhenius activation or by increased oxide fields following Multi-Phonon Field-Assisted Tunneling (MPFAT) theory. In both cases, the trapping times are sensitive to slight deviations in energy and thus the focus is on an accurate calculation of the band edge energy diagram. Therefore, it is of utmost importance to go beyond semiclassical parabolic band models and incorporate quantum mechanical effects, such as quantum confinement and exchange-correlation energy. Considering quantum confinement, the charge carriers are no longer assumed to be located at the band edge but are predominately situated in the first confined state. This confined state shifts away from the band edge for higher oxide fields and thus strongly affects the field dependence of NBTI. In addition, irrefutable exchange-correlation effects, such as those considered in accurate density functional theory simulations, move the position of the confined levels. Furthermore, a six-band k·p model was employed to consider the non-parabolicity of the density of states in the conduction band as well as in the valence band, which strongly impacts the band bending in the substrate. In light of these refinements, the temperature activation and the field acceleration of NBTI was thoroughly re-examined.