A semiconductor structure and a method for forming same are provided. In one form, a forming method includes: providing a base, where a core layer is formed on the base, a hard mask layer is formed on the core layer, and a first mask opening is formed in the hard mask layer; forming a first mask trench in the core layer exposed from the first mask opening, the first mask trench including a plurality of mask sub-trenches along an extending direction, where the mask sub-trenches are isolated from each other using the core layer exposed from the first mask opening; forming a first spacer on a side wall of the mask sub-trench; removing a core layer of a region in which the first mask opening is located, and forming, at a position corresponding to the core layer, a second mask trench enclosed by the first spacer and the base, the second mask trench and the first mask trench being isolated from each other using the first spacer; and forming a second spacer on a side wall of the second mask trench, where both the first spacer and the base, and the second spacer and the base, enclose a first target trench. The first spacer and the second spacer whose side walls contact with each other are used as a cutting member, alleviating rounding of a head of the first target trench.