Dielectric barrier layer for a copper plating layer having a varying across the thickness silicon concentration

A silicon nitride layer with a silicon-rich sub-layer and a default sub-layer is formed on a copper surface in order to obtain excellent electro-migration properties due to the standard part layer with the copper in contact, while improved diffusion barriers properties remain preserved due to the silicon-rich sub-layer. By combining these partial layers the total thickness of the silicon nitride layer can be kept small in comparison to conventional Siliziumnitridbarrierenschichten, whereby the capacitive coupling of adjacent copper wires is reduced.