To anodize a gate wiring composed of aluminum without forming an anodizing voltage supply line.

A Ta film/Al film is formed on a gate insulating film 103. The Al film is patterned to form an Al layer 106 by each gate wiring. Thus, all Al layers 106 are electrically short-circuited by the Ta film. The probe of an anodizing device is brought in contact with the Ta film to anodize the Al film 106 and the Ta film to form a barrier A.O. film 107 and a TaOx film 109. The Ta film which is not anodized functions as a Ta layer 108 of the gate wiring. Since the TaOx film 109 is formed on the entire surface of a substrate 100, the difference between heights due to the gate wiring is relaxed.