Silicon‐on‐insulator (SOI) structures, fabricated by laser annealing, were observed with cross‐sectional transmission electron microscopy. The film thickness was found to be almost uniform in SOI fabricated using a nonseeded Si3N4 antireflection film stripe technique, but some small mass transfer could be seen. Most of the crystal was of good quality, and almost no defects were observed, even in portions where stress was expected to be strongly exerted, such as at SOI/SiO2 interfaces or Si3N4 stripe edges. The defects which could be seen, however, were mostly those which had penetrated from the SOI/SiO2 interface to the SOI surface. Although the crystal quality was good, under relatively high laser power, dislocation loops were generated in the Si substrate. A grain boundary, generated from the deformed SOI/SiO2 interface, was also found. Furthermore, high‐resolutional lattice image observations carried out for the lateral seeding epitaxy SOI revealed that the abruptness at the SOI/SiO2 interface was rougher than that at the SiO2/Si substrate interface.