A method of fabricating a FinFET includes at last the following steps. A direction is determined by tilting 8.05±2 degrees from a normal vector of a (110) lattice plane of a semiconductor substrate. The semiconductor substrate is patterned along a lattice plane perpendicular to the direction, so as to form a plurality of trenches in the semiconductor substrate and at least one semiconductor fin having sidewalls disposed on a (551) lattice plane. Insulators are in the trenches. A gate stack is formed over portions of the semiconductor fin and over portions of the insulators. Strained material portions are formed over the semiconductor fins revealed by the gate stack.