Optical semiconductor device and fabrication method thereof

A method for fabricating an optical semiconductor device, comprising the steps of:

• (a) depositing a first semiconductor layer, an active layer, and a second semiconductor layer each of which is formed by a compound semiconductor that contains arsenic (As) alone as a group V element by crystal growth;
• (b) forming a striped stacking body by processing the first semiconductor layer, the active layer and the second semiconductor layer into a mesa shape such that a part of the first semiconductor layer remains on a surface of the semiconductor substrate;
• (c) raising a temperature to a crystal growth temperature in an atmosphere which includes arsenic, and then carrying out crystal growth to form a burying layer such that the burying layer buries the striped stacking body.