A semiconductor device comprises a first substrate portion and a second substrate portion disposed a distance away from the first substrate portion. The first substrate portion includes a first active semiconductor layer defining at least one semiconductor fin and a first polycrystalline layer formed directly on the fin. The first polycrystalline layer is patterned to define at least one semiconductor gate. The second substrate portion includes a doped region interposed between a second active semiconductor region and an oxide layer. The oxide layer protects the second active semiconductor region and the doped region. The doped region includes a first doped area and a second doped area separated by the first doped region to define a depletion region.