Dual side source/drain contact structures in semiconductor devices and method for forming the same

A semiconductor device, comprising:

• first and second source/drain regions;
• a contact structure, comprising:
• a silicide layer disposed on the first source/drain region,
• a silicide nitride layer disposed on the silicide layer, and
• a metal layer disposed on the silicide nitride layer;
• and
• a semiconductor layer disposed on the second source/drain region, wherein materials of the semiconductor layer and the second source/drain region are different from each other.

A method, comprising:

• forming first and second source/drain openings in a substrate;
• forming a sacrificial epitaxial layer on the substrate in the first source/drain opening;
• epitaxially growing first and second etch stop layers in the first and second source/drain openings, respectively;
• epitaxially growing first and second source/drain regions on the first and second etch stop layers, respectively;
• and
• replacing the sacrificial epitaxial layer and portions of the substrate overlapping the sacrificial epitaxial layer with a contact structure.