A plurality of device patterns constituting part of an electronic circuit are formed over the surface of a substrate. A symbol pattern to be used for an identification sign is formed in the same layer as the device patterns. A width of the device pattern is within a pattern width range on a design rule. The symbol pattern is formed by a plurality of isolated element patterns. The element pattern is either a linear pattern or a dot pattern. A width of the element pattern is equal to or larger than 0.8 time a lower limit value of the pattern width range and equal to or smaller than 1.2 times an upper limit value of the pattern width range.