Germanium on insulator (GOI) semiconductor substrates are generally described. In one example, a GOI semiconductor substrate comprises a semiconductor substrate comprising an insulative surface region wherein a concentration of dopant in the insulative surface region is less than a concentration of dopant in the semiconductor substrate outside of the insulative surface region and a thin film of germanium coupled to the insulative surface region of the semiconductor substrate wherein the thin film of germanium and the insulative surface region are simultaneously formed by oxidation anneal of a thin film of silicon germanium (Si1-xGex) deposited to the semiconductor substrate wherein x is a value between 0 and 1 that provides a relative amount of silicon and germanium in the thin film of Si1-xGex.