In some embodiments, a method for manufacturing forms a semiconductor device, such as a transistor. A dielectric stack is formed on a semiconductor substrate. The stack comprises a plurality of dielectric layers separated by one of a plurality of spacer layers. Each of the plurality of spacer layers is formed of a different material than immediately neighboring layers of the plurality of dielectric layers. A vertically-extending hole is formed through the plurality of dielectric layers and the plurality of spacer layers. The hole is filled by performing an epitaxial deposition, with the material filling the hole forming a wire. The wire is doped and three of the dielectric layers are sequentially removed and replaced with conductive material, thereby forming upper and lower contacts to the wire and a gate between the upper and lower contacts. The wire may function as a channel region for a transistor.