The article summarizes the development of metal gate materials and the control of the effective work function on high dielectric constant (high K) oxides for use in advanced Si field effect transistors. The Schottky barrier heights of metals on HfO2 are calculated accurately for ideal interfaces of various stoichiometries and for interfaces with defects. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3072517]