The crystallinity and regrowth mechanism of a seeded‐lateral epitaxial layer of Si on a SiO2substrate is evaluated using a newly developed microprobe reflection high‐energy electron diffraction method. Measurements with a spatial resolution of 0.1 &mgr;m reveal that the lateral seeding process actually occurs in the regrowth process and that the seeding area is indispensable to the process, though a seed length of less than 0.5 &mgr;m is required.