SEMICONDUCTOR STRUCTURE HAVING EPITAXIAL STRUCTURE

A semiconductor structure is provided. The semiconductor structure includes a first fin and a second fin on a semiconductor substrate. The semiconductor structure also includes an epitaxial structure on the first fin and the second fin. The semiconductor structure further includes outer spacers on outer sidewalls of the epitaxial structure. In addition, the semiconductor structure includes an inner spacer structure between the first fin and the second fin and covering inner sidewalls of the epitaxial structure. A top surface of the inner spacer structure is exposed to an air gap formed between the epitaxial structure and the inner spacer structure.