The invention provides a semiconductor structure and a forming method thereof, wherein, the method comprises the following steps: a substrate; a first well region, a second well region, a third well region and a fourth well region located between the third well region and the first well region which are located in the substrate, the third well region and the second well region being the same in conductivity type of doped ions and the fourth well region and the third well region being opposite in conductivity type of doped ions; a device structure located on the third well region; a first dopedregion and a second doped region located in the first well region, the first doped region and the second doped region being separate, the conductivity type of the doped ions in the first doped regionand the second doped region being opposite to that of the first well region, the first doped region being electrically connected to the device structure; a third doped region located in the second well region, the third doped region being electrically connected to the second doped region. The first doped region, the first well region and the second doped region form a transistor, which can improve the performance of the semiconductor structure.