To provide a method for producing an SOI substrate at lower cost without requiring any intermediate heat treatment.

After H ions and He ions are implanted into a silicon substrate with acceleration energy of 5-40 keV, temperature of the silicon substrate is raised to about 500°C and then O ions are implanted with acceleration energy of 30-180 keV thus forming an ion implantation layer 2. The silicon substrate is then heat treated at 1000°C-1400°C for an appropriate time to produce an ion implantation transition layer 3 including a plurality of voids 6, 6,... which are employed as heterogeneous nuclei of SiO2 phase in the formation of a buried oxide layer 4 and a surface silicon layer 5.