An electronic device includes a substrate, a first plate having a first internal surface facing a first surface of the substrate, and at least one first through-hole and at least one second through-hole, first and second semiconductor packages spaced apart from each other between the first surface and the first internal surface, a first thermal interface material layer contacting an upper surface of the first semiconductor package and the first internal surface, and filling at least a portion of the at least one first through-hole, and a second thermal interface material layer contacting an upper surface of the second semiconductor package and the first internal surface, and filling at least a portion of the at least one second through-hole. At least one of side surfaces of the first and second thermal interface material layers is exposed to an empty space between the first internal surface and the first surface.