A plurality of nanowires is grown on a first substrate in a first direction perpendicular to the first substrate. An insulation layer covering the nanowires is formed on the first substrate to define a nanowire block including the nanowires and the insulation layer. The nanowire block is moved so that each of the nanowires is arranged in a second direction parallel to the first substrate. The insulation layer is partially removed to partially expose the nanowires. A gate line covering the exposed nanowires is formed. Impurities are implanted into portions of the nanowires adjacent to the gate line.