A fuse element has a first region, a second region and a third region. The first region is a portion for isolating circuitry. The second region and the third region are respectively connected to both ends of the first region and have a wider pattern width than that of the first region. The second region, the first region and a part of the third region of the fuse element are formed on a thick insulating film, while the remaining part of the third region is formed on a thin insulating film. Heat generated in the fuse element is less likely to be released to a semiconductor substrate through the thick insulating film, but is more likely to be released to the semiconductor substrate through the thin insulating film. The fuse element therefore has a large temperature change and a large temperature gradient. This facilitates electrical blowing of the first region.