A semiconductor device includes: a first insulating layer with a flat surface formed over a semiconductor substrate structure in which a plurality of semiconductor elements are formed; column-like conductive plugs formed to penetrate the first insulating layer in the thickness direction; elongated wall-like conductive plugs formed through the first insulating layer in the thickness direction; a second insulating layer with a flat surface formed on the first insulating layer covering the column-like conductive plugs and the wall-like conductive plugs; and first wirings having dual damascene structures. Each of the first wirings has a first portion penetrating the second insulating layer in the thickness direction and connected to at least one of the columnar conductive plugs, and a second portion formed in the second insulating layer to an intermediate depth and apparently intersects at least one of the wall-like conductive plugs when viewed above.