Semiconductor device with back-side via structure

A semiconductor device comprising:

• a substrate having a first side and a second side opposite to each other;
• a transistor structure disposed on the first side of the substrate, and including a pair of epitaxial structures spaced apart from each other and a channel feature extending in a channel length direction to be disposed between the epitaxial structures;
• and
• a back-side via structure disposed on the second side of the substrate and extending through the substrate, the back-side via structure being connected to a corresponding one of the epitaxial structures and being formed with a recessed surface which is configured to be connected to a lower portion of the corresponding one of the epitaxial structures and which is recessed inwardly from an upper surface of the back-side via structure, the recessed surface having:
• a bottom surface portion connected to a bottom surface of the lower portion of the corresponding one of the epitaxial structures, and
• a first sidewall surface portion extending between the upper surface of the back-side via structure and the bottom surface portion of the recessed surface and connected to a first lateral surface of the lower portion of the corresponding one of the epitaxial structures.

A method for manufacturing a semiconductor device, comprising:

• forming a sidewall spacer to laterally cover a lower portion of an epitaxial structure of a transistor structure disposed on a first side of a substrate;
• conducting a first etching process to pattern the substrate and to selectively etch one of the sidewall spacer and the lower portion of the epitaxial structure so as to expose the lower portion of the epitaxial structure from an opening that is formed by the first etching process and that extends inwardly from a second side of the substrate opposite to the first side of the substrate;
• conducting a second etching process after the first etching process to selectively etch the other one of the sidewall spacer and the lower portion of the epitaxial structure;
• and
• filling a conductive material into the opening to form a back-side via structure disposed on the second side of the substrate and connected to the lower portion of the epitaxial structure.