Integrated circuit structure and manufacturing method thereof

A method for manufacturing an IC structure, comprising:

• forming a gate structure over a substrate;
• forming a plurality of spacers on opposite sides of the gate structure;
• etching a recess in the substrate and a side recess between the substrate and one of the spacers;
• forming a sacrificial epitaxial plug in the recess in the substrate;
• forming an epitaxial feature over the sacrificial epitaxial plug and filling the side recess;
• forming a source/drain epitaxial structure over the epitaxial feature;
• replacing the substrate with a dielectric layer;
• etching the sacrificial epitaxial plug and the epitaxial feature to form a backside via opening in the dielectric layer;
• and
• forming a backside via in the backside via opening.

A method for manufacturing an IC structure, comprising:

• forming a gate structure over a substrate;
• etching a recess in the substrate adjacent the gate structure;
• forming a sacrificial epitaxial plug in the recess in the substrate;
• forming a source/drain epitaxial structure over the sacrificial epitaxial plug, wherein the sacrificial epitaxial plug is between the source/drain epitaxial structure and a portion of the substrate in a vertical direction that is normal to a bottommost surface of the substrate;
• replacing the gate structure with a metal gate structure;
• and
• replacing the sacrificial epitaxial plug with a backside via.