Methods are presented for fabricating nanowire structures, such as one or more nanowire field effect transistors. The methods include, for instance: providing a substrate and forming a fin above the substrate so that the fin has a first sidewall including one or more elongate first sidewall protrusions and a second sidewall including one or more elongate second sidewall protrusions, with the one or more elongate second sidewall protrusions being substantially aligned with the one or more elongate first sidewall protrusions; and, anisotropically etching the fin with the elongate first sidewall protrusions and the elongate second sidewall protrusions to define the one or more nanowires. The etchant may be chosen to selectively etch along a pre-defined crystallographic plane, such as the (111) crystallographic plane, to form the nanowire structures.