Damascene wiring structure and semiconductor device with damascene wirings

A damascene wiring structure having: a lower wiring structure; an interlayer insulating film covering the lower wiring structure; a wiring trench formed in the interlayer insulating film from an upper surface thereof, and a via hole passing through the interlayer insulating film from a lower surface of the wiring trench in an inner area thereof and reaching the lower wiring structure, the via hole having a diameter smaller than a width of the wiring trench; an insulating pillar pattern projecting upward from the lower surface of the wiring trench in an area outside of the via hole, the insulating pillar pattern being made of a same material as the interlayer insulating film, wherein a first occupied area factor of the insulating pillar pattern in a first area of the wiring trench near said via hole is higher than a second occupied area factor of the insulating pillar pattern in a second area of the wiring trench remote from the via hole; and a dual damascene wiring formed by filling the wiring trench and said via hole with conductive material. A damascene wiring structure having a high reliability and a semiconductor device having such a damascene wiring structure can be formed.