Semiconductor device structure for chip identification

A semiconductor device, comprising:

• a first transistor on a substrate, wherein the first transistor comprises:
• a first channel structure on the substrate;
• a gate structure on the first channel structure;
• an epitaxial structure on the first channel structure at a first side of the gate structure;
• and
• a first source/drain (S/D) contact structure on the first channel structure at a second side of the gate structure opposite to the first side;
• and
• a second transistor on the substrate, wherein the second transistor comprises:
• a second channel structure on the substrate;
• the gate structure on the second channel structure;
• the epitaxial structure on the second channel structure at the first side of the gate structure;
• and
• a second S/D contact structure on the second channel structure at the second side of the gate structure, wherein the second S/D contact structure is separate from the first S/D contact structure.

A method, comprising:

• forming first and second channel structures on a substrate;
• forming a gate structure on the first and second channel structures;
• forming, at a first side of the gate structure, an epitaxial structure on the first and second channel structures;
• and
• forming, at a second side of the gate structure opposite to the first side, a first source/drain (S/D) contact structure on the first channel structure and a second S/D contact structure on the second channel structure, wherein the first and second S/D contact structures are separated from each other.