To suppress temperature rise at reflow heating without damaging the heat radiating characteristics when operation a semiconductor device.

An IC package 4 forms a gap 8 from the surface 6 of a main body 106 to cover the surface 6 of the main body 106, with a heat-insulating cover 10 absorbing or reflecting infrared ray provided. The heat-insulating cover 10 is fixed to the main body 106 by an adhesive agent 12 sticking to the four corners on the main body surface, wife contacting the main body surface by a minimum area. As a material for the heat-insulating cover, a card board, for example, comprising infinite voids inside a layer is used. An infrared ray 110 emitted for solder reflow is effectively prevented by the heat-insulating cover 10. The heat-insulating cover 10 fixed by the adhesive agent 12 is easily taken out, so, at operation of a semiconductor device, the heat-insulating cover 10 is taken out for assured heat-radiation characteristics.