PURPOSE: To optimize the shape, and improve the reliability, by flattening an insulating film by reflowing it at a first temperature, implanting impurity ion into the upper layer part of the insulating film, forming an aperture thereon, and then making only the upper layer part of the insulating film reflow at a second temperature lower than the first temperature.

CONSTITUTION: An insulating film 4 composed of glass containing impurity is formed on a substrate having a step-difference. This insulating film 4 is subjected to heat-treating at a first temperature and reflowing, and impurity ion is implanted in the upper layer part of the insulating film 4 to form an aperture part 5 in the insulating film 4. After heat treatment at a lower temperature than the first temperature, only the ion-implanted part of the insulating film 4 reflows, and a wiring 7 is formed in the aperture part 5. therefore, as to the part that reflows, the aperent W/D is increased, so that the aperture part 5 having an optimum shape in which only the upper layer part is tapered is obtained. Thereby, a highly reliable wiring can be formed.