Semiconductor structure and forming method thereof

The invention provides a semiconductor structure and a forming method thereof. The semiconductor structure comprises a semiconductor substrate which is provided with a fin part, wherein the fin part comprises a fin part first part; and a gate structure, wherein the gate structure stretches across the fin part first part and covers the top and the side wall of the fin part first part, grooves are formed in the fin part first parts on the two sides of the gate structure, and the width of the bottom face of each groove is smaller than that of the fin part. According to the semiconductor structure and the forming method thereof, by increasing the average distance between the epitaxial layer and the channel, stray capacitance and leakage current are reduced, and the reliability of a device is improved. 本申请提供一种半导体结构及其形成方法，所述半导体结构包括：半导体衬底，所述半导体衬底上形成有鳍部，所述鳍部包括鳍部第一部分；栅极结构，所述栅极结构横跨所述鳍部第一部分，且覆盖所述鳍部第一部分的顶部和侧壁，所述栅极结构两侧的鳍部第一部分中形成有凹槽，且所述凹槽底面的宽度小于所述鳍部的宽度。本申请提供的半导体结构及其形成方法通过增大外延层与沟道之间的平均距离，进而减少寄生电容和漏电流，提高器件的可靠性。