FORMATION OF WIRING

PURPOSE:To prevent a defect, of an element, caused by a cavity by a method wherein a substratum metal film is formed of a plated film only inside a via hole and a plated film is then formed on the rear surface of a substrate. CONSTITUTION:An Au/Ti film 13 as a substratum metal film whose bonding property with reference to Au is good is formed on the whole rear surface of a substrate 11 including a via hole 12; and a photoresist film 14 is left only inside the via hole 12. After that, also the Au/Ti film 13 on a sidewall near an opening of the via hole 13 is removed simultaneously by, e.g. an ion milling operation and, in addition, by implanting ions obliquely. An electric current is applied to a source pad 4 and to the Au/Ti film 13; an Au film 15 is precipitated inside the via hole 12 by an electrolytic plating method. When the Au film 15 is formed in advance only inside the via hole by the electrolytic plating method in this manner, the via hole can be filled completely with the Au film 15. Thereby, a cavity is not produced inside the via hole and a defect is not produced in a heat treatment during a post process.