To improve characteristics of a semiconductor device (semiconductor laser), an active layer waveguide (AWG) comprised of InP is formed over an exposed part of a surface of a substrate having an off angle ranging from 0.5° to 1.0° in a [1-1-1] direction from a (100) plane to extend in the [0-1-1] direction. A cover layer comprised of p-type InP is formed over the AWG with a V/III ratio of 2000 or more. Thereby, it is possible to obtain excellent multiple quantum wells (MQWs) by reducing a film thickness variation of the AWG. Moreover, the cover layer having side faces where a (0-11) plane almost perpendicular to a substrate surface mainly appears can be formed. A sectional shape of a lamination part of the cover layer and the AWG becomes an approximately rectangular shape. Therefore, an electrification region can be enlarged and it is possible to reduce a resistance of the semiconductor device.