Field effect transistor structures are described that are formed using germanium nanowires. In one example, the structure has a germanium nanowire formed on a substrate along a predetermined confinement orientation, a first doped region of the nanowire at a first end of the nanowire to define a source, a second doped region of the nanowire at a second end of the nanowire to define a drain, and a gate dielectric formed over the nanowire between the source and the drain.