Structure and Formation Method of Semiconductor Device with Backside Conductive Contact

A method for forming a semiconductor device structure, comprising:

• forming a fin structure over a substrate, wherein the fin structure has a plurality of sacrificial layers and a plurality of semiconductor layers laid out in an alternating manner;
• partially removing the fin structure to form an opening exposing side surfaces of the semiconductor layers and the sacrificial layers;
• partially removing the sacrificial layers from the side surfaces of the sacrificial layers to form recesses and a bottom recess;
• forming inner spacers in the recesses;
• forming a protective structure in the bottom recess;
• forming an epitaxial structure filling the opening;
• partially removing the substrate from a backside surface of the substrate to form a contact opening exposing the protective structure;
• and
• forming a backside conductive contact in the contact opening, wherein the backside conductive contact is electrically connected to the epitaxial structure.

A semiconductor device structure, comprising:

• a base semiconductor nanostructure;
• a plurality of semiconductor nanostructures over the base semiconductor nanostructure;
• a gate stack wrapped around each of the semiconductor nanostructures;
• an epitaxial structure connecting the semiconductor nanostructures;
• an inner spacer between the epitaxial structure and the gate stack;
• a backside conductive contact electrically connected to the epitaxial structure, wherein the backside conductive contact extends across opposite surfaces of the base semiconductor nanostructure;
• and
• a protective structure, wherein the base semiconductor nanostructure is between the protective structure and the semiconductor nanostructures.