Method for the formation of different gate metal regions of MOS transistors

A method for making an integrated circuit including at least two different gate metal regions of at least two MOS transistors, the method comprising:

• forming a metal layer with first and second regions on a gate dielectric layer above a substrate;
• forming a metal hard mask on the metal layer, the metal hard mask having a composition different from that of the metal layer, and covering the first region of the metal layer to define an intermediate structure and leaving open the second region of the metal layer;
• rapid thermal annealing the intermediate structure to make metal atoms of the metal hard mask diffuse into the first region of the metal layer, with the rapid thermal annealing being carried out in presence of a gaseous mixture comprising ammonia for nitriding the second region of the metal layer so as to increase a nitrogen concentration thereof;
• and
• removing the metal hard mask.

A method for making an integrated circuit including at least two different gate metal regions of at least two MOS transistors, the method comprising:

• forming a metal layer with first and second regions on a gate dielectric layer;
• forming a hard mask on the metal layer, the hard mask having a composition different from that of the metal layer, and covering the first region of the metal layer and leaving open the second region of the metal layer;
• and
• diffusing atoms of the hard mask into the first region of the metal layer, with the diffusion being carried out in presence of a gaseous mixture comprising ammonia for nitriding the second region of the metal layer so as to increase a nitrogen concentration thereof.