A method for manufacturing an integrated circuit (IC) structure is provided. The method includes: etching a first recess and a second recess in a substrate; forming a sacrificial epitaxial plug in the first recess in the substrate; forming a first epitaxial feature and a second epitaxial feature respectively in the first recess and the second recess, wherein the first epitaxial feature is over the sacrificial epitaxial plug; forming a first source/drain epitaxial structure and a second source/drain epitaxial structure over the first epitaxial feature and the second epitaxial feature respectively; forming a gate structure laterally between the first source/drain epitaxial structure and the second source/drain epitaxial structure; removing the sacrificial epitaxial plug and the first epitaxial feature to form a backside via opening exposing a backside of the first source/drain epitaxial structure; and forming a backside via in the backside via opening.