bonding a first single-crystal semiconductor substrate having a first oxide film on a major surface to a second single-crystal semiconductor substrate having a second oxide film on a major surface via the first and second oxide films while making the major surfaces oppose each other;

selectively etching the second single-crystal semiconductor substrate and part of a buried oxide film formed from the first and second oxide films from a surface opposite to the major surface of the second single-crystal semiconductor substrate to a halfway depth of the buried oxide film;

forming a sidewall insulating film on an etching side surface of the second single-crystal semiconductor substrate;

selectively etching the remaining buried oxide film except that immediately under the second single-crystal semiconductor substrate; and

forming a single-crystal semiconductor layer on the first single-crystal semiconductor substrate exposed by removing the buried oxide film,

wherein silicon is used as the first and second single-crystal semiconductor substrates and the single-crystal semiconductor layer, silicon oxide is used as the first and second oxide films, and first silicon nitride is used as the sidewall insulating film, and in selectively etching the second single-crystal semiconductor substrate and part of the buried oxide film, a second silicon nitride film is partially formed on the second single-crystal semiconductor substrate, and the second single-crystal semiconductor substrate and buried oxide film are selectively etched using the first and second silicon nitride films as a mask.