We report the fabrication of rhombohedral corundum-structured indium oxide (alpha-In2O3) thin films, which can complete a semiconductor quaternary alloy system with alpha-Al2O3 and alpha-Ga2O3, on sapphire substrates with alpha-Fe2O3 buffer layers. X-ray diffraction showed the formation of alpha-In2O3, and the alpha-In2O3 film exhibited n-type semiconductor properties with electron concentration of 1.2 x 10(18) cm(-3) and electron mobility of 83 cm(2)/Vs. The alpha-In2O3 took grain structure with the lateral sizes of 300-600 nm, and in a grain area alpha-In2O3 grew epitaxially on a sapphire substrate. (C) 2012 Elsevier B.V. All rights reserved.