The process mapping of the ALD process of HfO2 using HfCl4 and H2O is reported. A thickness uniformity better than 3% was achieved over a 300 mm-wafer at a deposition rate of 0.52 Å/cycle. Usually, H2O purge period is set less than 10 sec to obtain reasonable throughput; however, the amounts of residual impurities (Cl, H) found to be in the order of sub%, and these impurities are piled up near the HfO2/Si interface. In order to reduce the piled up impurities, we proposed a 2-step deposition in which purge period for initial 10-20 cycles was set to be 90 sec and that for remaining cycles was usual value of 7.5 sec. The leakage current is reduced to 1/10 by using this 2-step deposition.