A manufacturing method of a semiconductor device which includes wiring dense part and wiring isolated part enables occurrence of ‘Erosion’ to be prevented, as well as it is capable of being prevented occurrence of ‘micro-scratch’ on surface of oxide layer. The manufacturing method sets a plurality of trench-parts on insulation layer, before forming metal plating layer consisting of copper so as to embed trench-parts. Manufacturing process implements annealing in such a way that grain-size of the metal plating layer in the wiring dense part becomes smaller than the grain-size in the wiring isolated part. The annealing, for instance, is implemented with substrate temperature of 70 to 200° C. Subsequently, the manufacturing step perfects the semiconductor device while polishing the metal plating layer to cause the surface of the substrate to be flat.