conventionally , semiconductor devices wherein a flexible sheet with a conductive pattern was employed as a supporting substrate , a semiconductor element was mounted thereon , and the ensemble was molded have been developed . in this case , problems occur that a multilayer wiring structure cannot be formed and warping of the insulating resin sheet in the manufacturing process is prominent . in order to solve these problems , a laminated plate in which a thin first conductive film and a thick second conductive film have been laminated via a third conductive film is used . in a step for forming a conductive wiring layer by etching the first conductive film , etching depth can be controlled by stopping etching at the third conductive film . accordingly , forming the first conductive film to be thin makes it possible to form the conductive wiring layer into a fine pattern .