We have developed a modified technique to fabricate silicon-germanium on insulator (SGOI) starting with a sandwiched structure of Si/SiGe/Si. By means of oxidation and annealing, relaxed SiGe-on-insulator (SGOI) with a Ge fraction of 34% has been produced. Our results indicate that oxidation of. the silicon cap suppresses Ge loss at the initial stage of the SiGe oxidation and the subsequent annealing process homogenizes the Ge fraction and also reduces Ge enrichment under the oxide. It is found that the strain in the SiGe layer is almost fully relaxed at high oxidation temperature (similar to 1150 degrees C) without generating any dislocations and crosshatch patterns that are commonly observed on the surface of a relaxed or partially relaxed SiGe layer on bulk Si substrate. (c) 2005 American Vacuum Society.