Methods for fabricating semiconductor structures, such as fin structures of FinFET transistors, are provided. In one embodiment, a method comprises providing a semiconductor substrate and forming a plurality of mandrels overlying the semiconductor substrate. Each of the mandrels has sidewalls. L-shaped spacers are formed about the sidewalls of the mandrels. Each L-shaped spacer comprises a rectangular portion disposed at a base of a mandrel and an orthogonal portion extending from the rectangular portion. Each L-shaped spacer also has a spacer width. The orthogonal portions are removed from each of the L-shaped spacers leaving at least a portion of the rectangular portions. The semiconductor substrate is etched to form fin structures, each fin structure having a width substantially equal to the spacer width.