The new route to fabricate compositionally graded and highly-relaxed Si(1-x)Ge(x) layers using thermal oxidation at high temperatures is investigated Ge atoms behavior during thermal oxidation of Si(1-x)Ge(x) layers is strongly dependent on the oxidation temperature For low temperature oxidation processes Ge is incorporated as GeO(2) in the grown oxide layer. while for higher temperatures It accumulates below the grown oxide into a layer with a higher concentration than the initial Si(1-x)Ge(x). However, Si(1-x)Ge(x) layers oxidized at 1000 degrees C did not show such an accumulation layer because Ge diffusion efficiently occurred, resulting in the formation of a compositionally graded and relaxed Si(1-x)Ge(x) layer Such layers could be used as virtual substrates for the strained-Si and relaxed-SiGe applications (C) 2009 Elsevier B V All rights reserved