Interface formation between reactively sputtered tungsten nitride (WNx) or titanium nitride (TiNx) metallic films and thermally grown silicon dioxide (SiO2) layers is studied by interrupted growth with on-line Auger electron spectroscopy. For both composite metals, growth proceeds directly without a metal precursor layer. The chemical stability of these WNx/SiO2 and TiNx/SiO2 interfaces is investigated by rapid thermal annealing up to 850 degrees C. The WNx/SiO2 interface is stable up to 650 degrees C while TiNx/SiO2 is stable below 850 degrees C. Metal-oxide-semiconductor capacitors have been fabricated with WNx and TiNx gates and 7.5 nm thick thermal oxide gate dielectrics with interface trap densities, D-it<2X10(11) cm(-2)eV(-1). Capacitance-voltage and current-voltage measurements indicate the Fermi level for TiNx lies near midgap in Si, while for WNx it lies closer to the valence band.