Epitaxial gamma-Al2O3(1 I 1) films on Si(1 1 1) substrates were grown with very smooth surfaces using Al-N2O mixed source molecular beam epitaxy. The deposition was performed on chemically oxidized Si(1 I I) substrates without employing any severe surface-cleaning process. Epitaxial gamma-Al2O3 films were obtained at substrate temperatures of above 650 degrees C with very smooth surface. Comparing gamma-Al2O3 films deposited on chemically oxidized and HF-treated substrates, it was considered that a chemical oxide layer acts as a protection layer for the surface against etching caused by the N2O environment gas. In addition, no interface oxide layer was observed between the grown Al2O3 layer and the Si substrates after Al2O3 growth. Because of its simplicity, this method is useful for adapting crystalline gamma-Al2O3 films into Si ultra-large-scale integrated circuit applications. (c) 2006 Elsevier B.V. All rights reserved.