An interlayer insulator includes a first interlayer insulator and a second interlayer insulator formed on the first interlayer insulator and having a property of preventing diffusion of copper. A barrier metal film is formed on an inner wall in the wiring trench except an upper end and operative to prevent copper contained in the Cu wiring from diffusing into the interlayer insulator. The Cu wiring is brought into contact with the second interlayer insulator at the upper end and covered with the barrier metal film at a lower portion below the upper end.
