A semiconductor laser device includes: a semiconductor laminate body; an insulating layer disposed above the semiconductor laminate body and including a first opening extending in a first direction that is a direction from a front end surface toward a rear end surface; a first electrode disposed above the semiconductor laminate body; a second electrode disposed above the first electrode and the insulating layer; and an adhesion layer disposed between the second electrode and the insulating layer. The adhesion layer includes a second opening that at least partially overlaps with the first opening in plan view, the first electrode is at least partially disposed inside the first opening and the second opening, and the second electrode and the adhesion layer are disposed above the insulating layer between the first opening and at least one of the front end surface or the rear end surface.

A semiconductor device is provided. The semiconductor device includes a first semiconductor structure, a second semiconductor structure on the first semiconductor structure and an active structure between the first semiconductor structure and the second semiconductor structure. The first semiconductor structure includes a first waveguiding layer having a first band gap, and a first interlayer directly contacting the first waveguiding layer and having a first thickness and a second bandgap lager than the first band gap. The first thickness is 5 nm-35 nm.

Provided here are: a mesa strip which has an n-type cladding layer, an active layer and a p-type cladding layer that are stacked sequentially on a surface of an n-type substrate; Fe-doped semi-insulating layers which are embedded along both sides of the mesa stripe, each up to a height higher than the mesa stripe; n-type blocking layers which are stacked on respective surfaces of the Fe-doped semi-insulating layers located on the both sides of the mesa stripe, and which are spaced apart from each other with an interval that is a space corresponding to a central portion of the active layer and is thus narrower than the active layer; p-type cladding layers which are formed on back surfaces of respective mesa-stripe-side end portions of the n-type blocking layers; and a p-type cladding layer which buries a top of the mesa stripe, the p-type cladding layers and the n-type blocking layers.