An embodiment of the invention provides a method for forming a semiconductor structure. The method includes forming a first active fin structure and a second active fin structure on a substrate. A dummy fin structure is formed on the substrate, the dummy fin structure being interposed between the first active fin structure and the second active fin structure. The dummy fin structure is removed toexpose a first portion of the substrate, the first portion of the substrate being disposed directly below the dummy fin structure. A plurality of protruding features is formed on the first portion ofthe substrate. A shallow trench isolation (STI) region is formed over the first portion of the substrate, the STI region covering the plurality of protruding features, at least a portion of the firstactive fin structure and at least a portion of the second active fin structure extending above a topmost surface of the STI region. The embodiment of the invention also provides a semiconductor structure.