In this work, we investigated the epitaxial growth of Gd2O3 thin films on germanium layers grown by surfactant-mediated epitaxy on silicon (001) substrates. The influence of the lattice mismatch between Ge and Gd2O3 as Well as the impact of the lower surface energy of Ge compared to Si on the growth process have been studied resulting in conditions for epitaxy of smooth Gd2O3 films without any interfacial layer on Ge. We determined the epitaxial relationship and the crystalline structure of these films using transmission electron microscopy and X-ray diffraction. The Gd2O3 layers grow in two orthogonal (011)-oriented domains of the cubic phase. They are relaxed and show structural perfection similar to that of Gd2O3 films grown on Si(001). No interfacial layer is observed between the Gd2O3 and Ge making this material combination particularly suitable for an application in high-mobility channel MOSFETs with equivalent oxide thickness below 1 nm. (C) 2009 Elsevier Ltd. All rights reserved.