A semiconductor structure includes a semiconductor substrate, a dielectric structure formed on the semiconductor substrate and including at least a recess formed therein, a fin formed in the recess, and a dislocation region formed in the fin. The semiconductor substrate includes a first semiconductor material. The fin includes the first semiconductor material and a second semiconductor material. A lattice constant of the second semiconductor material is different from a lattice constant of the first semiconductor material. A topmost portion of the dislocation region is higher than an opening of the recess.