Semiconductor transistor device includes backside via electrically connecting epitaxial source/drain structures and method for forming the same

Abstract

A method includes forming a semiconductor strip and semiconductor layers vertically stacked over a front side of the semiconductor strip; forming a gate structure over the semiconductor layers; etching the semiconductor strip to form recesses in the semiconductor strip and on opposite sides of the gate structure; forming epitaxial layers in the recesses, respectively; forming isolation layers over the epitaxial layers, respectively; forming epitaxial source/drain structures over the isolation layers, respectively; performing an etching process from a backside of the semiconductor strip to form a via opening extending through the semiconductor strip, one of the epitaxial layer, and one of the isolation layer, wherein one of the epitaxial source/drain structures is exposed through the via opening; and forming a backside via in the via opening.