Optical semiconductor device

An optical semiconductor device comprising:

• a first optical device formed on a silicon substrate having a first surface;
• and
• a second optical device including a compound semiconductor, mounted on the first optical device, and having a second surface facing the first surface, wherein:
• the first optical device includes a first protrusion that protrudes toward the second surface,
• the second optical device includes a second protrusion that protrudes toward the first surface and makes contact with the first protrusion,
• a portion of the second surface makes contact with the first protrusion,
• in a plan view, the first and second protrusions have a planar shape having a first direction as a longitudinal direction of the first and second protrusions and a second direction perpendicular to the first direction as a short direction of the first and second protrusions, and the first protrusion is located on an inner side of an outer edge of the second optical device,
• in a cross section perpendicular to the first direction, a width of the first protrusion along the second direction is greater than a width of the second protrusion along the second direction, and
• in the plan view, outer edges of the first protrusion on two opposite ends of the first protrusion along the first direction are not aligned to outer edges of the second protrusion on two opposite ends of the second protrusion along the first direction.