Patent ID: 8617954

Claim:
A method for manufacturing a semiconductor device including SiON gate dielectrics of different thicknesses, comprising: providing a substrate comprising silicon and a protective layer exposing a higher voltage device region of the substrate and covering a lower voltage device region of the substrate; with the protective layer covering the lower voltage device region, subjecting the exposed higher voltage device region to a first plasma nitridation to form a nitrogen region in the higher voltage device region; with the protective layer still covering the lower voltage device region, growing a first thickness of nitrided SiO 2 dielectric material on the exposed higher voltage device region by oxidizing silicon in the nitrogen region using at least one of N 2 O or NO gas; following growing the first thickness, removing the protective layer from the lower voltage device region; with the protective layer removed from the lower voltage device region, growing a second thickness of nitrided SiO 2 dielectric material on the first thickness on the exposed higher voltage device region and on the lower voltage device region; and following growing the second thickness, subjecting the dielectric material on the higher voltage device region and on the lower voltage device region to a second plasma nitridation; whereby a SiON gate dielectric with a substantially uniform nitrogen concentration throughout a bulk region of the combined first and second thicknesses is formed on the higher voltage device region.