Non-volatile semiconductor storage device and method of manufacturing the same

A non-volatile semiconductor storage device comprising:

• a plurality of memory strings each having a plurality of electrically rewritable memory cells connected in series,
• each of the memory strings comprising:
• a first semiconductor layer including a columnar portion extending in a vertical direction with respect to a substrate;
• a plurality of first conductive layers formed to surround side surfaces of the columnar portions via insulation layers, and formed at a certain pitch in the vertical direction, the first conductive layers functioning as floating gates of the memory cells;
• and
• a plurality of second conductive layers formed to surround the first conductive layers via insulation layers, and functioning as control electrodes of the memory cells,
• the first conductive layers being formed of polysilicon.

A method of manufacturing a non-volatile semiconductor storage device having a plurality of memory strings each having a plurality of electrically rewritable memory cells connected in series, the method comprising:

• forming a plurality of first conductive layers above a substrate via first interlayer insulation layers;
• forming a first hole to penetrate the plurality of first conductive layers and the first interlayer insulation layers;
• sequentially forming a second conductive layer and a first semiconductor layer on a side surface of the first hole, the second conductive layer surrounded by an insulation layer;
• forming a first trench to penetrate the plurality of first conductive layers and the first interlayer insulation layers, the first trench extending in a first direction parallel to the substrate;
• removing the first interlayer insulation layers via the first trench to form air gaps between the first conductive layers aligned in a vertical direction with respect to the substrate;
• and
• oxidizing parts of the second conductive layers via the first trench and the air gaps.