In order to provide excellent device characteristics and enhance fabrication yield and run-to-run reproducibility in a buried device structure using a low mesa on a p-type substrate, a cross sectional configuration before growth of a contact layer of a device, i.e., after growth of an over-cladding layer is flattened so as not to cause a problem in crystal quality of the contact layer. A mesa-stripe stacked body including at least a p-type cladding layer (2), an active layer (4) and an n-type cladding layer (6) is formed on a p-type semiconductor substrate (1), a current-blocking layer (8) is buried in both sides of the stacked body, and an n-type over-cladding layer (9) and an n-type contact layer (10) are disposed on the current-blocking layer (8) and the stacked body. The n-type over-cladding layer (9) is made of a semiconductor crystal having a property for flattening a concavo-convex shape of upper surfaces of the current-blocking layer (8) and the stacked body.