Suppression of boron penetration for p/sup +/ stacked poly-Si gates by using inductively coupled N2 plasma treatment

Nitridation of stacked poly-Si gates by inductively coupled N/sub 2/ plasma (ICNP) treatment has been shown to suppress boron penetration and improve gate oxide integrity. The ICNP treatments on the stacked poly-Si layers create nitrogen-rich layers not only between the stacked poly-Si layers but also in the gate oxide after post implant anneal, thus resulting in effective retardation of boron diffusion. In addition, positioning of ICNP treatment closer to gate oxides leads to higher nitrogen peaks in the gate oxide region, resulting in further suppression of boron penetration and improvement of gate oxide reliability.