Abstract: A method to improve silicon oxynitride when used as an etching stop for silicon oxide plasma etching, by nitridizing with a nitrogen plasma, in the fabrication of an integrated circuit is achieved. The method is applied to forming etch stopping silicon oxynitride spacers for MOS transistors and for forming etch stopping silicon oxynitride for dual damascene interconnects. A semiconductor substrate is provided wherein devices and features have been formed in and on the semiconductor substrate. A silicon oxynitride layer is deposited overlying the semiconductor substrate. The silicon oxynitride layer is nitridized. An interlevel dielectric oxide layer is deposited overlying surface of the silicon oxynitride layer. The interlevel dielectric oxide layer is etched through to the silicon oxynitride layer where defined by photolithography and wherein the silicon oxynitride layer acts as an etching stop.