Abstract: Semiconductor devices may be fabricated using nanowires. In an example embodiment, a conductive gate may be used to control conduction along the nanowires, in which case one of the contacts is a drain and the other a source. The nanowires may be grown in a trench or through-hole in a substrate or in particular in an epitaxial layer on substrate. In another example embodiment, the gate may be provided only at one end of the nanowires. The nanowires can be of the same material along their length; alternatively different materials can be used, especially different materials adjacent to the gate and between the gate and the base of the trench.