A conductive layer which is formed on an insulative layer on a semiconductor substrate is connected to the semiconductor substrate via a through portion which passes through the insulative layer and reaches the semiconductor substrate. In a state where the conductive layer is electrically connected to the semiconductor substrate via the through portion, a patterning process using a plasma etching is performed on the conductive layer, thereby forming a conductive path. After the formation of the conductive path, a heating process is performed on the substrate or the conductive path in order to disconnect the electrical connection between the through portion and the substrate by a reaction between the through portion and the semiconductor substrate which is in contact therewith.