  Ab initio techniques are used to calculate the effective work function (Weff)
of a TiN/HfO2/SiO2/Si stack representing a metal-oxide-semiconductor (MOS)
transistor gate taking into account first order many body effects. The required
band offsets were calculated at each interface varying its composition. Finally
the transitivity of LDA calculated bulk band lineups were used and completed by
MBPT bulk corrections for the terminating materials (Si and TiN) of the MOS
stack. With these corrections the ab initio calculations predict a Weff of a
TiN metal gate on HfO2 to be close to 5.0 eV.
