We have characterized HfO2 thin films grown by source gas pulse introduced metallorganic chemical vapor deposition (MOCVD) technique using Hf(O-t-C4H9)(4) as a Hf precursor, and H2O or O-2 as an oxidization gas. The Hf precursor and H2O (or O-2) were alternately introduced with N-2 purge step, which is one growth cycle in this experiment. The residual impurity concentration in HfO2 thin films can be reduced when the film is grown by pulse-MOCVD using H2O. In addition, the leakage current density has been improved for the HfO2 film grown with H2O. This low leakage current density is considered to be due to the lower impurity concentration in the film grown with H2O as an oxidization gas. (C) 2004 The Electrochemical Society.