A unique process for the preparation of high permittivity metal oxide by direct thermal reaction of metal on SiO2 is described. The samples prepared by this new process exhibit excellent electrical characteristics, including high capacitance, low leakage current, and low interface state density. In addition, the electrical characteristics of the metal/oxynitride stack are superior to that of a metal/oxide stack. The improvement of electrical characteristics of metal/oxynitride stack can be explained by less metal penetration through the oxynitride layer, which was confirmed by transmission electron microscopy and energy dispersive X-ray analysis.