A process for passivating the semiconductor-dielectric interface of a MOS structure to reduce the interface state density to a very low level. A particular example is a MOSFET having a tungsten electrode that in the past has prevented passivation of the underlying semiconductor-dielectric interface to an extent sufficient to reduce the interface state density to less than 5×1010/cm2−eV. Though substantially impervious to molecular hydrogen, thin tungsten layers are shown to be pervious to atomic hydrogen, enabling atomic hydrogen to be diffused through a tungsten electrode into an underlying semiconductor-dielectric interface. Three general approaches are encompassed: forming an aluminum-tungsten electrode stack in the presence of hydrogen so as to store atomic hydrogen between the tungsten and aluminum layers, followed by an anneal to cause the atomic hydrogen to diffuse through the tungsten layer and into the interface; subjecting a tungsten electrode to hydrogen plasma, during which atomic hydrogen diffuses through the electrode and into the semiconductor-dielectric interface; and implanting atomic hydrogen into tungsten electrode, followed by an anneal to cause the atomic hydrogen to diffuse through the electrode and into the semiconductor-dielectric interface.