A method for manufacturing a semiconductor device of one embodiment of the present invention includes: forming an insulation layer to be processed over a substrate; forming a first sacrificial layer in a first area over the substrate, the first sacrificial layer being patterned to form in the first area a functioning wiring connected to an element; forming a second sacrificial layer in a second area over the substrate, the second sacrificial layer being patterned to form in the second area a dummy wiring; forming a third sacrificial layer at a side wall of the first sacrificial layer and forming a fourth sacrificial layer at a side wall of the second sacrificial layer, the third sacrificial layer and the fourth sacrificial layer being separated; forming a concavity by etching the insulation layer to be processed using the third sacrificial layer and the fourth sacrificial layer as a mask; and filling a conductive material in the concavity.