PURPOSE: To avoid the damage of a layer insulation film on a fuse after fusing by a method wherein the fusing part of the poly Si fuse is covered with an SiO2 film or a dense insulation film adhered after removing the SiO2 film.

CONSTITUTION: The conductive poly Si film 3 of a pattern having a terminal part 12 and the fusing part 11 is formed on an Si substrate 1 via the SiO2 film 2. When the SiO2 thick film 17 is formed only at the fusing part 11' by being covered with an SiO2 thin film 14, superposing an Si3N4 film 15, and opening a window through the film 15, the fuse of small fusing current can be obtained without increasing the resistance of the slender part. The film 15 is removed by etching and covered with an SiO2 18, and Al electrodes 19 and 19' and an SiO2 protection film 20. Or, after patterning the fuse, a part of the slender part 11 is left and covered with an Si3N4, and accordingly a thick film which is dense and good adhesion property can be formed by thermally oxidizing the aperture. This constitution enables to avoid the damage of the insulation film on the fuse after fusing by decreasing the fusing voltage without increasing fuse resistance to a large extent.