Selective formation of titanium silicide and titanium nitride by hydrogen gas control

A semiconductor device, comprising:

• a substrate;
• a fin structure disposed on the substrate;
• a source/drain region disposed on the fin structure;
• a metal silicide layer disposed on the source/drain region;
• a metal nitride layer disposed on the metal silicide layer;
• a curved interface between the metal silicide layer and the metal nitride layer, wherein a curvature of the curved interface faces the metal nitride layer;
• a conductive layer disposed on the metal nitride layer;
• and
• a gate spacer disposed on sidewalls of the metal silicide layer and the metal nitride layer.

A semiconductor device, comprising:

• a substrate;
• a fin structure disposed on the substrate;
• a source/drain region disposed in the fin structure;
• a silicide layer disposed on the source/drain region;
• a nitride layer, disposed on the silicide layer, comprising a protruding surface between a sidewall surface and a bottom surface of the nitride layer, wherein the bottom surface of the nitride layer is disposed at a surface plane above a top surface of the fin structure;
• and
• a metal layer disposed on the nitride layer.