The present invention provides a light-emitting semiconductor device, which comprises a substrate having a surface formed with a plane and a plurality of protrusions out of the plane. The plane is on a crystalline orientation. The protrusion is provided with an outer surface consisting of a plurality of sidewall surfaces. The sidewall surfaces are substantially not on the crystalline orientation. The protrusion is formed with an outline edge extended from the bottom to the top of the protrusion from a side view. The outline edge comprises at least one turning point. A first conductive type semiconductor layer is above the surface of the substrate, an active layer is above the first conductive type semiconductor layer, and a second conductive type semiconductor layer is above the active layer.