Semiconductor structure and forming method thereof

The invention provides a semiconductor structure and a forming method thereof. The semiconductor structure comprises a semiconductor substrate, a fin is formed on the semiconductor substrate, and the fin comprises a first part and a second part; the semiconductor substrate further comprises a dielectric layer covering the side wall and the top surface of the second part of the fin, a gate layer covering part of the dielectric layer and a hard mask layer covering the top surface of the gate layer; the semiconductor structure also comprises a side wall which is located on the side wall of the gate layer; and an epitaxial layers which are located in the fins on the two sides of the gate layer and protrude out of the fins, wherein gaps exist between the portions, protruding out of the fins, of the epitaxial layers and the gate layer. According to the semiconductor structure and the forming method thereof, stray capacitance between the epitaxial layer and the grid electrode is reduced by increasing the distance be