Multi-silicide system in integrated circuit technology

An integrated circuit comprising:

• a semiconductor substrate;
• a gate dielectric on the semiconductor substrate;
• a gate over the gate dielectric;
• a shallow source/drain junction in the semiconductor substrate using the gate;
• a sidewall spacer around the gate;
• a deep source/drain junction in the semiconductor substrate using the sidewall spacer;
• a cobalt silicide over the deep source/drain junction, the cobalt silicide being formed from cobalt of a thickness under 10 Angstroms;
• a nickel silicide over the cobalt silicide, the nickel silicide being formed from nickel of a thickness such that the cobalt silicide blocks diffusion of the nickel silicide into the semiconductor substrate;
• a dielectric layer above the semiconductor substrate;
• and
• a contact in the dielectric layer to the nickel silicide.