An Si crystal film functioning as a channel region is formed on an SiGe crystal film substrate. Furthermore, an SiGe crystal film functioning as a channel region is formed on the Si crystal film. In addition, on the opposite sides of the SiGe crystal film and the Si crystal film, an Si crystal film functioning...http://www.google.se/patents/US6825507?utm_source=gb-gplus-sharePatent US6825507 - Semiconductor device having high electron mobility comprising a SiGe/Si/SiGe substrate
