Y2O3 thin films have been deposited on (100) Si substrates by r.f.-magnetron sputtering and subsequently submitted to rapid thermal processing (RTP). X-ray examinations show that the sputtered Y2O3 was dominated by the (111) cubic structure. With increasing RTP temperature (>700 degrees C), the crystallinity of films was improved, especially for the intensity of (400) diffraction peak. The as-deposited films show good dielectric properties in terms of a relative dielectric constant of 16.67 and leakage current density of 6x10(-7) A cm(-2) (at 1.8 MV cm(-1)). After the RTP treatment, both the dielectric constant and leakage current of Y2O3 were found to decrease. A typical dielectric constant decreased to 14.77 and its leakage current density lowered to 3 x 10(-8) A cm(-2) (at 1.8 MV cm(-1)) for the film annealed at 850 degrees C. The observed behavior of dielectric constant may be due to the intermediate oxide formation between Y2O3 and Si. Capacitance-voltage characteristics confirm that the reduction of leakage current at high electric field comes from the improvement of interface states.