To reduce the chip size of a semiconductor device by narrowing wiring intervals.

After an Al-Si-Cu dummy pattern 32 is formed on an insulating film 30 formed on a semiconductor substrate, an insulating layer 34 is formed on the pattern 32. Then lower-layer wiring 36 having a protrusion 40 at the position corresponding to the pattern 32 is formed on the insulating layer 34, After the wiring 36 is covered with an interlayer insulating film 38, the protrusion 40 of the wiring 36 is exposed by polishing the interlayer insulating film 38 to a flat surface. Thereafter, a titanium nitride(TiN) film 50 is etched off and upper-layer wiring 42 is formed in such a way that the wiring 42 is connected to the second metallic film 48 of the exposed protrusion 40.