A method for fabricating a semiconductor structure includes forming a plurality of initial fin structures on a substrate, each including a first region used as a first fin structure, a second region on the first region, and a third region on the second region; forming a first isolation layer on the substrate; removing each third region to form a first opening in the first isolation layer; forming a second isolation layer on sidewall surfaces of each first opening; and removing each second region to form an initial second opening; performing an etching process on the first isolation layer on sidewall surfaces of each initial second opening to form a second opening; forming a second fin structure in each first opening and the second opening; and removing a portion of the first isolation layer and the second isolation layer to expose a portion of sidewall surfaces of each second fin structure.