The present invention is directed to improved dielectric copper barrier layer and related interconnect structures. One structure includes a semiconductor substrate having a copper line. An insulating layer formed of at least one of silicon and carbon is formed on the underlying copper line. An opening is formed in the insulating layer to expose a portion of the copper line. The inner surface of the opening in the insulating layer has a dielectric barrier layer formed thereon to prevent the diffusion of copper into the insulating layer. A copper plug is formed to fill the opening and make electrical contact with the underlying copper interconnect structure. Aspects of the invention also include methods for forming the dielectric copper barrier layers and associate copper interconnects to the underlying copper lines.