Lu2O3 thin films with a high dielectric constant (high k value) deposited on n-Si(100) were investigated. A capacitance equivalent thickness of 1.6 nm with a leakage current density of 1.2 × 10-3 A/cm2 (at +1 V) was obtained for 4.5 nm thick Lu 2O3 deposited at room temperature followed by postdeposition annealing (PDA) at 400°C in N2. The surface morphology for 8-20 nm thick Lu2O3 films became rough after the PDA process because of the crystallization, whereas the surface of 4.5 nm thick Lu2O3 was smooth even after the PDA process. No frequency dependence in the capacitance-voltage curve was observed, and its relative dielectric constant was 11. The hygroscopic properties of the Lu 2O3 thin films seemed to be superior to those of other rare-earth oxide thin films, probably due to Lu2O3 having the largest lattice energy among the rare-earth oxides.