Fin formation by epitaxial deposition

Methods of forming a fin structure for a field effect transistor are described. The methods may include the operations of patterning a mandrel on a surface of a substrate, and depositing an epitaxial layer of high-mobility channel material over exposed surfaces of the patterned mandrel. The epitaxial layer leaves a gap between adjacent columns of the patterned mandrel, and a dielectric material may be deposited in the gap between the adjacent columns of the patterned mandrel. The methods may also include planarizing the epitaxial layer to form a planarized epitaxial layer and exposing the columns of the patterned mandrel, and etching at least a portion of the exposed columns of the patterned mandrel and the dielectric material to expose at least a portion of the planarized epitaxial layer that forms the fin structure.