Ultrahigh density vertical NAND memory device
Monolithic, three dimensional NAND strings include a semiconductor channel, at least one end portion of the semiconductor channel extending substantially perpendicular to a major surface of a substrate, a plurality of control gate electrodes having a strip shape extending substantially parallel to the major surface of the substrate, the blocking dielectric comprising a plurality of blocking dielectric segments, a plurality of discrete charge storage segments, and a tunnel dielectric located between each one of the plurality of the discrete charge storage segments and the semiconductor channel.
1. A monolithic three dimensional NAND string, comprising:
a semiconductor channel located over a substrate, the semiconductor channel having a U-shaped side cross section, wherein two wing portions of the U-shaped semiconductor channel which extend substantially perpendicular to a major surface of the substrate are connected by a connecting portion which extends substantially parallel to the major surface of the substrate;
an insulating fill located over the connecting portion and separating two wing portions of the U-shaped semiconductor channel;
a plurality control gate electrodes having a strip shape extending substantially parallel to the major surface of the substrate, wherein the plurality of control gate electrodes comprise at least a first control gate electrode located in a first device level and a second control gate electrode located in a second device level located over the substrate and below the first device level;
a plurality of blocking dielectric segments, wherein each of the plurality of blocking dielectric segments is located in contact with a respective one of the plurality of control gate electrodes;
a plurality of discrete charge storage segments; and
a tunneling dielectric located between the plurality of discrete charge storage segments and the semiconductor channel.
2. The monolithic three dimensional NAND string of claim 1 , wherein at least a portion of each of the plurality of blocking dielectric segments has a clam shape and wherein each of the plurality of discrete charge storage segments is located at least partially in an opening of a respective clam-shaped blocking dielectric segment.
3. The monolithic three dimensional NAND string of claim 1 , wherein the plurality of discrete charge storage segments comprise a plurality of floating gates.
4. The monolithic three dimensional NAND string of claim 1 , wherein the plurality of discrete charge storage segments comprise a plurality of discrete charge storage dielectric features.
5. The monolithic three dimensional NAND string of claim 4 , wherein:
each of the plurality of discrete charge storage dielectric features comprises a nitride feature located in the respective clam-shaped blocking dielectric segment; and
the blocking dielectric segment, the nitride feature and the tunnel dielectric form oxide-nitride-oxide discrete charge storage structures of the NAND string.
6. The monolithic three dimensional NAND string of claim 1 , further comprising one of a source or drain electrode contacts the first wing portion of the semiconductor channel from above, and another one of a source or drain electrode which contacts the second wing portion of the semiconductor channel from above.
7. The monolithic three dimensional NAND string of claim 6 , further comprising a body contact electrode which contacts the connecting portion of the semiconductor channel from below.