It is an object of the present invention to provide a method for preventing a breaking and poor contact, without increasing the number of steps, thereby forming an integrated circuit with high driving performance and reliability. The present invention applies a photo mask or a reticle each of which is provided with a diffraction grating pattern or with an auxiliary pattern formed of a semi-translucent film having a light intensity reducing function to a photolithography step for forming wires in an overlapping portion of wires. And a conductive film to serve as a lower wire of a two-layer structure is formed, and then, a resist pattern is formed so that a first layer of the lower wire and a second layer narrower than the first layer are formed for relieving a steep step.