Semiconductor device and method for fabricating the same

A semiconductor device, comprising:

• a gate structure on a substrate;
• a source/drain region adjacent to two sides of the gate structure;
• a contact plug adjacent to the gate structure and on the source/drain region, wherein the contact plug comprises:
• an epitaxial layer on the source/drain region;
• an interface layer on the epitaxial layer, wherein the interface layer comprises silicon germanium;
• a first silicide layer on the interface layer;
• a second silicide layer on the first silicide layer, wherein both the first silicide layer and the second silicide layer comprise an I-shape;
• a barrier layer on the second silicide layer;
• and
• a conductive layer on the barrier layer.