To prevent an influence from being exerted on a main light shielding pattern by causing a defect only at an auxiliary pattern part even when the pattern of a photomask is electrified and electrostatic discharge failure occurs.

The auxiliary patterns 3 and 4 are added to two adjacent main patterns 1 and 2 forming a semiconductor circuit. A distance (a) between the patterns 3 and 4 is the same as a distance (b) between the main patterns 1 and 2 but wiring width of the auxiliary pattern is 1/4 of that of the main pattern, so that electric field is easily concentrated most at the part of the patterns 3 and 4 and the electrostatic discharge failure occurs when a potential difference is made by the electrification. Even when the defect is caused on the light shielding pattern, the main pattern is normal, whereby the required semiconductor circuit is accurately formed.