Semiconductor structure and forming method thereof

A forming method of a semiconductor structure, comprising:

• providing a substrate and a gate structure, wherein the gate structure is located on the substrate;
• performing ion implantation on the substrate to form a plurality of doped regions in the substrate, wherein the doped regions are located at two sides of the gate structure;
• wherein one of the plurality of doped regions comprises a first doped region and a second doped region, a concentration of doped ions in the first doped region is greater than a concentration of doped ions in the second doped region, and the first doped region is far farther from a sidewall of the gate structure than the second doped region;
• removing part of the substrate, to form a trench, wherein the trench exposes a sidewall of the first doped region far from the gate structure;
• forming an electrical contact layer, wherein the electrical contact layer fills up the trench and is in contact with the sidewall of the first doped region far from the gate structure, and a top surface of the electrical contact layer is higher than a surface of the substrate;
• and
• forming a dielectric layer, wherein the dielectric layer fills a space between the electrical contact layer and the gate structure.