A method for fabricating a semiconductor device includes providing a semiconductor structure including a semiconductor substrate, a plurality of semiconductor fin structures, and a trench insulation layer formed on the semiconductor substrate and surrounding each semiconductor fin structure. The semiconductor fin structures include a plurality of first semiconductor fin structures and a plurality of second semiconductor fin structures. The top surface of the trench insulation layer is leveled with the top surface of the semiconductor fin structures. The method includes performing a first anti-punch-through doping process on the first semiconductor fin structures to form a first anti-punch-through region in each first semiconductor fin structure, removing a portion of each second semiconductor fin structure to form a trench, and forming an epitaxial layer on the remaining portion of the second semiconductor fin structure and a second anti-punch-through region in the epitaxial layer or in the remaining second semiconductor fin structure.