A semiconductor device with a structure having superior heat sink characteristics. A first heat sink member is located over a wiring board by using an adhesive material. A semiconductor element is stuck over the first heat sink member by using an adhesive material. The semiconductor element and electrodes located over the wiring board are connected by wires. A second heat sink member which covers the semiconductor element and the wires is joined to the first heat sink member by using a conductive adhesive material. The inside and outside of the second heat sink member are sealed by resin except a flat top thereof. By doing so, the semiconductor device is fabricated. Heat which is generated in the semiconductor element and which is transmitted to the first heat sink member is released from an edge portion of the first heat sink member. In addition, the heat which is generated in the semiconductor element and which is transmitted to the first heat sink member is transmitted to the conductive adhesive material and the second heat sink member and is released from the flat top of the second heat sink member.