In a semiconductor device according to the present invention, a plurality of opening regions 5 to 8 are formed in an insulating film on a pad electrode 3. A metal layer 9 formed on the pad electrode 3 has a plurality of concave portions 10 to 13 formed therein by covering the opening regions 5 to 8. Moreover, in a peripheral portion at a bottom of each of the concave portions 10 to 13 in the metal layer 9, the metal layer 9 and a Cu plating layer 19 react with each other. By use of this structure, the metal reaction area serves as a current path on the pad electrode 3. Thus, a resistance value on the pad electrode 3 is reduced.