A semiconductor structure and a method for fabricating the semiconductor structure are provided. The method includes providing a semiconductor substrate including a dense region and a sparse region. The method also includes forming initial fins equally spaced apart from one another on the semiconductor substrate, the initial fins including a plurality of intrinsic fins and dummy fins. The intrinsic fins on the dense region has a spatial density greater than the intrinsic fins on the sparse region. In addition, the method includes forming a first isolation layer on the semiconductor substrate. The first isolation layer covers a portion of sidewalls of the dummy fins and a portion of sidewalls of the intrinsic fins. Further, the method includes forming first trenches in the first isolation layer by removing the dummy fins, and forming a second isolation layer in the first trenches.