A method of forming a three-dimensional transistor device. The method may include providing a fin array on a substrate, the fin array comprising a plurality of fin structures, formed from a monocrystalline semiconductor, and disposed subjacent to a hard mask layer. The method may include directing angled ions at the fin array, wherein the angled ions form a non-zero angle of incidence with respect to a perpendicular to a plane of the substrate. The angled ions may etch the plurality of fin structures to form a stack of isolated nanowires, within a given fin structure.