PURPOSE: To obtain the SOI single crystal having a large area by a method wherein the pattern of a reflection preventing film and the method of scanning of a laser beam are specifically prescribed.
CONSTITUTION: The silicon nitride film 4, which is turned to a reflection preventing film, located on a strip-formed region 7 is removed by etching, an island is formed on the region other than the region 7 by performing an etching, an Ar gas laser beam having the beam width wider than the width of the region 7 is scanned on the region 7 along its longitudinal direction, a polysilicon film 3 is fused, and an annealing is performed. The growth of crystal is started from the inside of the region 7 and it makes progress toward the outside, and the silicon film 3 in the region 7 is single-crystallized. Then, a beam is scanned in the direction vertical to the longitudinal direction, the polysilicon film 3 located on the region other than the region 7 is fused, and an annealing is performed. The growth of crystal makes progress along the crystal growing direction 8, and when the temperature of the entire wafer drops, the growth of crystal makes progress along the direction 9. As all the regions are single- crystallized in the same degree as the single crystal region 7, the SOI film having no crystal grain boundary can be formed.
