A semiconductor device includes a substrate including a first region and a second region that are arranged in a first direction that is parallel to an upper surface of the substrate; a separation layer provided on the first region of the substrate; a high electron mobility transistor (HEMT) device overlapping the separation layer in a second direction that is perpendicular to the upper surface of the substrate; a light-emitting device provided on the second region of the substrate; and a first insulating pattern covering a side surface of the HEMT device, wherein the first insulating pattern overlaps the separation layer in the second direction.