High-k HfO2 dielectric films were grown by an atomic layer deposition (ALD) technique using HfCl4 and H2O on bare Si and various Al2O3-passivated Si wafers. The Al2O3 films were grown by different ALD processes using trimethylaluminum as the Al precursor and remote O-2 plasma, H2O, and O-3, as the oxidants. The electrical and structural properties of the stacked films were compared. O-3 appeared to be the most appropriate oxidant for growing Al2O3 films as the interlayer with superior quality and thermal stability due to its high oxidation power. The O-3-Al2O3/HfO2 stack exhibited an extremely low leakage current density suggesting its significance as a gate dielectric film for future field effect transistors. However, the stacked films with O-2 plasma or H2O grown Al2O3 layer showed an unstable flatband behavior and serious charge injection properties that precluded their adoption to metal-oxide-semiconductor field effect transistor devices. (c) 2005 The Electrochemical Society.