A method is disclosed to form a metal-oxysilicate diffusion barrier for a damascene metallization. A trench is formed in an Inter Layer Dielectric (ILD) material. An oxysilicate formation-enhancement layer comprising silicon, carbon, oxygen, a constituent component of the ILD, or a combination thereof, is formed in the trench. A barrier seed layer is formed on the oxysilicate formation-enhancement layer comprising an elemental metal selected from a first group of elemental metals in combination with an elemental metal selected from a second group of elemental metals. An elemental metal in the second group is immiscible in copper or an alloy thereof, has a diffusion constant greater than a self-diffusion of copper or an alloy thereof; does not reducing silicon-oxygen bonds during oxysilicate formation; and promotes adhesion of copper or an alloy of copper to the metal-oxysilicate barrier diffusion layer. The structure is then annealed to form a metal-oxysilicate diffusion barrier.