Embedded interconnections of copper are formed by forming an insulating layer, forming embedded interconnections of copper in the insulating layer, making an exposed upper surface of the insulating layer and an exposed surface of the embedded interconnections of copper coplanar according to chemical mechanical polishing, and forming a protective silver film on the exposed surface of the embedded interconnections of copper. These steps are repeated on the existing insulating layer thereby to produce multiple layers of embedded interconnections of copper. The exposed surface of the embedded interconnections of copper is plated with silver according to immersion plating.