Wet-NO oxidation with or without wet NH 3 pretreatment is used to grow GeON gate dielectric on Ge substrate. As compared to dry NO oxidation, negligible growth of GeO x interlayer and, thus, a near-perfect GeON dielectric can be obtained by the wet-NO oxidation. As a result, MOS capacitors prepared by this method show greatly reduced interface-state and oxide-charge densities and gate-leakage current. This should be attributed to the hydrolyzable property of GeO x in water-containing atmosphere.