Gate stack structure with oxygen gettering layer

A structure comprising:

• a substrate;
• a channel region in said substrate;
• source and drain regions in said substrate on opposite sides of said channel region;
• and
• a gate stack contacting said substrate above said channel region,
• wherein said gate stack comprises:
• an interface layer contacting said channel region of said substrate;
• a high-k dielectric layer having a dielectric constant above 4.0 contacting said interface layer;
• a metal Nitride layer contacting said dielectric layer;
• and
• a Polysilicon cap contacting said metal Nitride layer,
• wherein said metal Nitride comprises a graded amount of metal and Nitrogen such that a lower portion of said metal Nitride layer adjacent said high-k dielectric comprises excess Nitrogen and an upper portion of said metal Nitride layer adjacent said Polysilicon cap comprises excess metal.