A multi-layered metal line of a semiconductor device and a process of forming the same are described. The multi-layered metal line includes a lower metal line formed on a semiconductor substrate. An insulation layer is subsequently formed on the semiconductor substrate including the lower metal line and has an upper metal line forming region that exposes a portion of the lower metal line. A diffusion barrier formed on a surface of the upper metal line forming region of the insulation layer. The diffusion barrier includes a W—B—N ternary layer. An upper metal line is finally formed on the diffusion barrier to fill the upper metal line forming region of the insulation layer.