Electrical properties of CeO2 films prepared by reactive dc sputtering on Si(100) substrate with and without the incorporation of a thin barrier layer were investigated. X-ray diffraction spectra revealed that without the thin barrier layer, single-crystal CeO2 is formed on Si(100) substrate. At an equivalent oxide thickness of 2.8 nm, CeO2 films exhibit a leakage current which is four orders of magnitude lower than that of the conventional SiO2 film at an applied bias of 2 V. Only negligible stress-induced leakage current is observed after high field stressing. The incorporation of the thin silicon nitride buffer layer, however, degraded the crystalline structure of CeO2, accompanied by deteriorated electrical properties such as leakage current and fixed charges. CeO2 film without the barrier layer is thus attractive as the high dielectric constant gate insulator for future ultralarge scale integration devices.