This study describes deposition of HfO2 thin films by chemical vapor deposition (CVD) and atomic layer deposition (ALD) using HfI4 as the metal precursor. The layer-by-layer growth was also studied in real time with a quartz crystal microbalance. In ALD, the deposition rate was independent of the growth temperature, whereas in CVD, an exponential rate increase was observed. Monoclinic HfO2 was deposited on MgO and poly-Si substrates in a wide temperature range, and the choice of substrate had a strong influence on the orientation of the films. Epitaxial growth of HfO2 was observed on MgO(001) substrates at 400-500degreesC in the ALD process and at 500-600degreesC in the CVD process. The electrical characterization showed that the crystallinity of the films had a stronger influence on the dielectric constant than did the film thickness.