Tantalum oxide films were deposited using KrF excimer laser ablation of a Ta target and a Ta2O5 target in 5 mass% O-3 gas. The 5 mass% O-3 gas was used to improve the O/Ta ratio of the films. The tantalum oxide film properties such as transparency and corrosion resistance were then evaluated. The O/Ta ratio of the films deposited using Ta target were much improved by using 5 mass% O-3 gas at pressure lower than I Pa. There was no difference in the O/Ta atomic ratio of the film deposited in 5 mass% O-3 gas, although the Ta target as well as Ta2O5 target was used. The XPS spectrum of the oxidized layer of Ta surface at 5 mass% O-3 gas pressure of 5 Pa shifted to a higher binding energy than that in O-2 gas. The transparency of the films deposited in both 5 mass% O-3 gas and O-2 gas increased steeply at a O/Ta ratio of 2. The transparency of the stoichiometric films became as high as 90%. The corrosion resistance of the stoichiometric film was as high as the passive film of the Ta plate in the 3.5 mass% NaCl solution. (C) 2002 Elsevier Science B.V. All rights reserved.