Semiconductor device and manufacturing method thereof

A semiconductor device, comprising:

• a substrate;
• a gate structure over the substrate;
• source/drain regions in the substrate and on opposite sides of the gate structure;
• a source/drain contact over one of the source/drain regions;
• a metal cap over the source/drain contact;
• a contact plug over the metal cap, wherein the contact plug is in contact with at least three sides of the metal cap in a cross-sectional view;
• a first etch stop layer extending from a sidewall of the metal cap to a sidewall of the contact plug;
• a second etch stop layer over the first etch stop layer;
• and
• an interlayer dielectric layer over the second etch stop layer, wherein the second etch stop layer and the interlayer dielectric layer are in contact with the sidewall of the contact plug.

A method, comprising:

• forming a gate structure over a substrate;
• forming source/drain regions over the substrate and on opposite sides of the gate structure;
• forming a source/drain contact over one of the source/drain regions;
• forming a protective cap over the gate structure;
• forming a first etch stop layer over the protective cap;
• forming a metal cap over the source/drain contact, wherein the metal cap is in contact with the protective cap and the first etch stop layer;
• and
• forming a contact plug over the metal cap and in contact with the first etch stop layer.