Patent ID: 6670695
Filing Date: 2003-12-30
Classification: G03F,H01L

Abstract:
A polysilicon gate of a MOS transistor, comprising:an oxide layer, over a silicon substrate; a polysilicon layer, over the oxide layer; a tungsten silicide layer, over the polysilicon layer; a graded silicon oxynitride layer, over the tungsten silicide layer, wherein the graded silicon oxynitride layer, comprising: an oxygen-rich silicon oxynitride layer; a nitrogen-rich silicon oxynitride layer; and a stack of silicon oxynitride layers between the oxygen-rich silicon oxynitride layer and the nitrogen-rich silicon oxynitride layer, wherein a silicon oxynitride layer in the stack closest to the oxygen-rich silicon oxynitride layer has a highest oxygen concentration and a silicon oxynitride layer in the stack closest to the nitrogen-rich silicon oxynitride layer has a highest concentration of nitrogen; and a silicon nitride layer, over the graded oxynitride layer.