Methods of forming semiconductor structures

A semiconductor structure comprising:

• an n transistor comprising first dielectric sidewalls defining a filled first opening over a first source/drain material on a substrate, the filled first opening comprising a first gapfill material;
• a p transistor comprising second dielectric sidewalls defining a filled second opening over a second source/drain material on the substrate, the filled second opening comprising a second gapfill material;
• a first titanium silicide (TiSi) layer directly on the first source/drain material;
• a second titanium silicide (TiSi) layer directly on the second source/drain material;
• a first barrier layer lining the filled first opening directly on the first dielectric sidewalls and directly on the first titanium silicide (TiSi) layer;
• a first molybdenum silicide (MoSi) layer directly on the first barrier layer in the filled first opening;
• a second molybdenum silicide (MoSi) layer lining the filled second opening directly on the second dielectric sidewalls, and directly on the second titanium silicide (TiSi) layer;
• and
• a second barrier layer directly on the first molybdenum silicide (MoSi) layer and directly on the second molybdenum silicide (MoSi) layer, wherein the second barrier layer is configured to prevent oxide formation on the first molybdenum silicide (MoSi) layer and on the second molybdenum silicide (MoSi) layer.