Oxygen ion is implanted into a silicon substrate to remain a silicon layer on a surface of the silicon substrate. In this state, a silicon oxide layer is formed under the silicon layer. Silicon oxide particles are formed and remained in the residual silicon layer. While maintaining this state, the silicon substrate is heated to a predetermined temperature not less than 1300.degree. C. Alternatively, the silicon substrate is heated at a high temperature-rise rate to 900.degree.-1100.degree. C., and thereafter is heated at a low temperature-rise rate to the temperature not less than 1300.degree. C. The silicon substrate is held at the predetermined temperature not less than 1300.degree. C. for a predetermined time, whereby crystallinity of the residual silicon layer is restored. A pinning effect of the silicon oxide particles prevents the rise of dislocation to the surface of the SOI layer, and also suppresses a rate per a unit time at which interstitial silicon generates during the heating to the high temperature region. Therefore, a dislocation density of the SOI layer can be reduced.