US Patent 9412821 Stacked thin channels for boost and leakage improvement

A hollow-channel memory device comprises a source layer, a first hollow-channel pillar structure formed on the source layer, and a second hollow-channel pillar structure formed on the first hollow-channel pillar structure. The first hollow-channel pillar structure comprises a first thin channel and the second hollow-channel pillar structure comprises a second thin channel that is in contact with the first thin channel. In one exemplary embodiment, the first thin channel comprises a first level of doping; and the second thin channel comprises a second level of doping that is different from the first level of doping. In another exemplary embodiment, the first and second levels of doping are the same.