A method for producing optical semiconductor devices includes: forming a stacked semiconductor layer on a device substrate to provide an epitaxial substrate having a size corresponding to a section arrangement; forming, on the epitaxial substrate, a mask having a pattern for a semiconductor mesa and for a trench of at least one optical semiconductor device, a width of the trench in the pattern being determined according to a trench width map in which trench width is based upon an in-plane distribution of the thickness of a resin layer of the at least one device, and upon a correlation between the thickness of the resin layer and the trench width; forming a trench structure including the semiconductor mesa and the trench by etching the stacked semiconductor layer using the mask; forming a resin layer on the trench structure; and forming an opening on the semiconductor mesa by etching the resin layer.