Physical and electrical properties of CeO 2 thin film deposited on p-type silicon substrate via the RF magnetron sputtering technique after treating in argon ambient at different annealing temperatures has been investigated and reported. Thickness of the CeO 2 thin film was in the range of 30–40nm measured by an ellipsometer at 5 different points for each sample. Post-deposition annealing was executed in argon ambient for 30min at four different temperatures (400, 600, 800, and 1000°C). The physical results demonstrated that the thin film was free of physical defects and root-mean square surface roughness decreased as the annealing temperature increased. X-ray diffraction indicated the occurrence of CeO 2 phase with four diffraction planes [(111), (200), (220), and (311)]. All samples showed negative flat band voltage shift owing to the existence of positive effective oxide charges. Samples annealed at 1000°C showed the lowest interface trap density, total interface trap density, effective oxide charge, and the highest barrier height. This attributed to the lowest leakage current density (∼1×10 −9 Acm −2 ) and the highest electric breakdown voltage (∼30V) of the sample when a comparison was made.