Non-volatile semiconductor storage device and method of manufacturing the same
A non-volatile semiconductor storage device has a plurality of memory strings with a plurality of electrically rewritable memory cells connected in series. Each of the memory strings comprises: a first columnar semiconductor layer extending in a vertical direction to a substrate; a charge accumulation layer formed around the first columnar semiconductor layer via a first insulation layer; and a first conductive layer formed around the charge accumulation layer via a second insulation layer. Each of the first conductive layers is formed to expand in a two-dimensional manner, and air gaps are formed between the first conductive layers located there above and there below.
1. A non-volatile semiconductor storage device comprising a plurality of memory strings with a plurality of electrically rewritable memory cells connected in series,
each of the memory strings comprising:
a first columnar semiconductor layer extending in a vertical direction to a substrate;
a charge accumulation layer formed around the first columnar semiconductor layer via a first insulation layer; and
a first conductive layer formed around the charge accumulation layer via a second insulation layer,
each of the first conductive layers being formed to expand in a two-dimensional manner, and
air gaps being formed between the first conductive layers located there above and there below.
2. The non-volatile semiconductor storage device according to claim 1 , wherein
each of the air gaps has partially provided therein an insulative fluid with lower permittivity than silicon oxide, or a solid insulation layer with lower permittivity than silicon oxide.
3. The non-volatile semiconductor storage device according to claim 1 , wherein
surfaces of the first conductive layers are silicided.
4. The non-volatile semiconductor storage device according to claim 2 , wherein
surfaces of the first conductive layers are silicided.
5. The non-volatile semiconductor storage device according to claim 1 , further comprising:
a first selection transistor connected to one end of each of the memory strings,
wherein each of the first selection transistors comprises:
a second columnar semiconductor layer in contact with the bottom surface of the first columnar semiconductor layer and extending in the vertical direction; and
a second conductive layer formed around the second columnar semiconductor layer via a third insulation layer.
6. The non-volatile semiconductor storage device according to claim 5 , further comprising:
a second selection transistor connected to the other end of each of the memory strings,
wherein each of the second selection transistors comprises:
a third columnar semiconductor layer in contact with the top surface of the first columnar semiconductor layer and extending in the vertical direction; and
a third conductive layer formed around the third columnar semiconductor layer via a fourth insulation layer.
7. The non-volatile semiconductor storage device according to claim 1 , wherein
the first conductive layers and the first columnar semiconductor layers are composed of polysilicon,
the first insulation layers are composed of silicon oxide,
the second insulation layers are composed of aluminum oxide, and
the charge accumulation layers are composed of silicon nitride.
8. The non-volatile semiconductor storage device according to claim 5 , wherein
the second conductive layers and the second columnar semiconductor layers are composed of polysilicon, and
the third insulation layers are composed of silicon oxide.
9. The non-volatile semiconductor storage device according to claim 6 , wherein
the third conductive layers and the third columnar semiconductor layers are composed of polysilicon, and
the fourth insulation layers are composed of silicon oxide.