Auger electron spectroscopy, energy electron loss spectroscopy, atomic force microscopy and transmission electron microscopy were used to characterize ultra-thin aluminum oxide films grown on hydrogen-terminated Si(0 0 1)-H substrates via a specific atomic layer deposition and oxidation technique. Oxide thin films grown in such a way are highly stable with temperature at least up to 700 degrees C. Band gap was estimated to be 6.6 +/- 0.2eV, independent of thickness. Formation of the oxide layer slightly increases the initial roughness of silicon surface. Furthermore, no silicon oxide was found at the aluminum oxide-silicon interface. (c) 2007 Elsevier B.V. All rights reserved.