Provided are an interconnection of a semiconductor device which includes a capping layer and a method for forming the interconnection. The interconnection of the semiconductor device is a copper damascene interconnection where the capping layer is formed as a dual layer of a silicon nitride layer and silicon carbide layer on a copper layer processed by chemical mechanical polishing (CMP). Therefore, it is possible to maintain a high etching selectivity and a low dielectric constant of the silicon carbide layer while providing superior leakage suppression.