For example, a metal foil such as a copper foil and an aluminum foil, and a film made of a resin such as polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polyimide and polyethylene may be used as the releasable carriers 31A and 31B. [0235] The wiring layer 21A is formed on the surface of the releasable carrier 31A by a method wherein an appropriate metal foil is superposed on the sur