ABSTRACT100 μm-wide silicon-on-insulator (SOI) structures have been accomplished by utilizing silicon molecular beam epitaxial (Si-MBE) growth on porous silicon anid subsequent lateral-enhanced oxidation of porous silicon through pattern widows. A silicon beam method was used for insitu cleaning of Si surface at 750°C, and the effectiveness of this method was demonstrated by Auger electron spectroscopy and checked by the etch-pit density of the grown film. A two-step growth process of Si MBE was used to grow epitaxial layers of high quality. An electron mobility of 1300 cm2V-1s-1 was obtained by van der Pauw measurements.