The materials characteristics of Al2O3 films grown on Si (100) substrate by traveling wave reactor atomic layer deposition were investigated at the growth temperature ranging from 250 to 500°C. The Al2O3 films grown using Al(CH3)3(TMA) and H2O as precursors were characterized and also compared with the films grown using AlCl3 and H2O. In the study of impurity incorporation, the films grown using TMA showed the C and H count rates of secondary ion mass spectrometry (SIMS) approximately 7–10 times higher than those of the film grown using AlCl3. For the Al2O3 films grown using TMA, the impurity contents and the growth rate decreased and the refractive index increased as increasing the growth temperature. The effect of purge time increase on the impurity incorporation was very small compared with that of growth temperature. The refractive indices were 1.64 and 1.68 at the growth temperatures of 250 and 400°C, respectively. The rough estimation using SIMS data and refractive indices indicated that the H-content decreased from 8.6 at% to 2.9 at% as increasing the substrate temperature from 250 to 400°C. The Al2O3 film grown using AlCl3 and H2O at 500°C contained approximately 0.5% Cl and revealed the refractive index of 1.65.