Optical semiconductor device, optical integrated device, and manufacturing method for optical semiconductor device

A manufacturing method for an optical semiconductor device, comprising:

• forming, on a substrate having a (100) face as a surface, a laminate structure in which a plurality of semiconductor layers is layered in a first direction, the plurality of semiconductor layers including a first semiconductor layer that is made of a material functioning as an active layer;
• forming a plurality of mesas protruding from the substrate at a plurality of locations separated in a second direction intersecting with the first direction by partially removing the laminate structure on an opposite side of the substrate;
• forming a current inhibition layer in order to fill space among the plurality of mesas;
• forming a conductor layer on the opposite side of the substrate with reference to the first semiconductor layer;
• forming a first protrusion including
• a first mesa representing one of the plurality of mesas,
• a part of the current inhibition layer that is adjacent to the first mesa, and
• a part of the conductor layer that is present on opposite side of the substrate with reference to the first mesa;
• and
• forming a second protrusion by performing etching, in which a predetermined etching solution or a predetermined etching gas is used, with respect to a second mesa that is one of the plurality of mesas other than the first mesa, wherein
• the forming of the plurality of mesas includes forming the second mesa by performing etching using a mask, and
• in planar view from an opposite direction of the first direction, the mask has a polygonal shape with each side being non-parallel to a virtual line extending in [0-11] direction.