Optical semiconductor device and method for manufacturing the same

A method for manufacturing an optical semiconductor device, the method comprising:

• forming, on a substrate having first and second regions adjacent to each other, a lower cladding layer, a lower optical guide layer formed of AlGaInAs, an active layer having a multiple quantum well structure in which a barrier layer formed of AlGaInAs and a well layer are alternately stacked, an upper optical guide layer formed of InGaAsP, and an upper cladding layer in this order;
• selectively forming a mask layer on the upper cladding layer in the first region;
• selectively etching at least the upper cladding layer in the second region which is not covered with the mask layer;
• leaving a first optical semiconductor element in the first region by selectively removing at least the active layer and the lower optical guide layer in the second region which is not covered with the mask layer by wet etching, the first optical semiconductor element being formed of at least the substrate, the lower cladding layer, the lower optical guide layer, the active layer, the upper optical guide layer, and the upper cladding layer;
• forming a second optical semiconductor element adjacent to the first optical semiconductor element on the lower cladding layer in the second region after the wet etching;
• and
• removing the mask layer.