Disclosed are a semiconductor structure and a method for forming the same. The method includes: providing a base, including a first region and a second region, where a pitch between target patterns formed on the first region is greater than a pitch between target patterns formed on the second region; forming a bottom core material layer on the base; forming first core layers on the bottom core material layer; forming a first mask sidewall on a sidewall of the first core layer of the first region, and forming a second mask sidewall on a sidewall of the first core layer of the second region, where the thickness of the second mask sidewall is greater than the thickness of the first mask sidewall; removing the first core layers; patterning the bottom core material layer by using the first mask sidewall and the second mask sidewall as masks, to form a second core layer; removing the first mask sidewall and the second mask sidewall; forming a third mask sidewall on a sidewall of the second core layer; removing the second core layer; and patterning the base by using the third mask sidewall as a mask, to form target patterns protruding out of a residual base. The present disclosure meets the requirement of different pitches of the target patterns.