A method of making a semiconductor device including a metal gate electrode on a semiconductor substrate with a silicon oxynitride spacer formed on a surface of the metal gate electrode, wherein an interface of the silicon oxynitride spacer and the metal gate electrode is substantially free of metal silicide. The process includes steps of forming a metal gate electrode on a semiconductor substrate; forming by PECVD on a surface of the metal gate electrode a silicon oxynitride spacer, wherein the silicon oxynitride spacer is formed under initially silicon-starved conditions in which a first quantity of at least one silicon-containing material is provided to a PECVD apparatus which is reduced relative to an amount of at least one other reactant, as a result of which substantially no silicide is formed.