A composite dielectric layer and method of forming the composite dielectric layer for the passivation of exposed copper in a copper damascene structure are described. The composite layer consists of a passivation dielectric layer and an etch stop dielectric layer and is formed over the exposed copper prior to the deposit of an inter-metal or final passivating dielectric layer. Via holes are etched in the inter-metal or final passivating layer and the composite dielectric layer provides an etch stop function as well as passivation for the exposed copper conductor. A thin layer of passivation dielectric, such as silicon nitride, is formed directly over the exposed copper to passivate the copper. A thin layer of etch stop dielectric, such as silicon oxynitride, is then formed over the layer of passivation dielectric. The passivation dielectric is chosen for passivation properties and adhesion between the passivation dielectric and copper. The etch stop layer is chosen for etch stop properties. The composite layer is thinner than would be required if the layer of passivation dielectric also provided the etch stop function so that circuit capacitance is reduced by using the composite layer.