Ultrathin SiGe films on insulator, with high Ge fraction, are fabricated through Ge condensation. A two-step oxidation process is pursued where temperatures chosen are lower than that corresponding to the solidous curve of the Si-Ge phase diagram. In this way, the smallest achievable thickness could be decreased further compared to a single step oxidation process. We achieved a uniform Ge fraction of 0.6 at a SiGe thickness of 6 nm, indicating a ten-fold increase in Ge fraction as compared to starting epitaxial SiGe layer. The surface roughness was below 1 nm and XRD analysis indicates that the films are compressive. © 2005 The Electrochemical Society. All rights reserved.