A semiconductor device includes a semiconducting substrate having CMOS transistors thereon. A composite etch stop layer including a lowermost silicon oxynitride portion and an uppermost silicon nitride portion is disposed on the semiconducting substrate including the CMOS transistors. At least one dielectric layer is on the composite etch stop layer. A first contact opening extends to a first level through the composite etch stop layer thickness and a second contact opening extends to a second level deeper than the first level through the composite etch stop layer.