Vertically-integrated nonvolatile memory devices having laterally-integrated ground select transistors
Nonvolatile memory devices utilize vertically-stacked strings of nonvolatile memory cells (e.g., NAND-type strings) that can be selectively coupled to common source lines within a substrate. This selective coupling may be provided by lateral ground select transistors having different threshold voltages that account for different lateral spacings between the vertically-stacked strings of nonvolatile memory cells and the common source lines.
1. A nonvolatile memory device, comprising:
a first common source line of first conductivity type within a semiconductor substrate;
a first NAND-type string of nonvolatile memory cells on the semiconductor substrate, said first NAND-type string comprising:
a first vertically-stacked plurality of nonvolatile memory cells;
a first ground select transistor electrically coupled in series with the first vertically-stacked plurality of nonvolatile memory cells; and
a first lateral ground select transistor having a source terminal within said first common source line and a drain terminal electrically connected to a source terminal of the first ground select transistor; and
a second NAND-type string of nonvolatile memory cells on the semiconductor substrate, said second NAND-type string comprising:
a second vertically-stacked plurality of nonvolatile memory cells;
a second ground select transistor electrically coupled in series with the second vertically-stacked plurality of nonvolatile memory cells; and
a second lateral ground select transistor having a source terminal electrically connected to the drain terminal of the first lateral enhancement-mode ground select transistor and a drain terminal electrically connected to a source terminal of the second ground select transistor, said second lateral ground select transistor having a lower threshold voltage relative to the first lateral ground select transistor.
2. The memory device of claim 1 , wherein said first common source line comprises a region of first conductivity type within a region of second conductivity type; and wherein a channel region of said first lateral ground select transistor is more heavily doped with second conductivity type dopants relative to a channel region of the second lateral ground select transistor.
3. The memory device of claim 2 , wherein a net conductivity type of the channel region of the second lateral ground select transistor is of first conductivity type.
4. The memory device of claim 2 , wherein the channel region of the second lateral ground select transistor comprises a region of first conductivity type.
5. The memory device of claim 2 , wherein the channel region of the second lateral ground select transistor comprises a region of first conductivity type and a region of second conductivity type.
6. A nonvolatile memory device, comprising:
first and second common source lines of first conductivity type within a semiconductor substrate;
a plurality of lateral ground select transistors electrically connected in series and having commonly-connected gate electrodes, said plurality of lateral ground select transistors comprising:
a first lateral ground select transistor having a source terminal within said first common source line;
a second lateral ground select transistor having a source terminal within said second common source line; and
a third lateral ground select transistor having a threshold voltage lower than a threshold voltage of at least one of the first and second lateral ground select transistors;
a first NAND-type string of vertically-stacked nonvolatile memory cells on the semiconductor substrate, said first NAND-type string comprising a first ground select transistor having a source terminal electrically connected to a drain terminal of the first lateral ground select transistor;
a second NAND-type string of vertically-stacked nonvolatile memory cells on the semiconductor substrate, said second NAND-type string comprising a second ground select transistor having a source terminal electrically connected to a drain terminal of the second lateral ground select transistor; and
a third NAND-type string of vertically-stacked nonvolatile memory cells on the semiconductor substrate, said third NAND-type string comprising a third ground select transistor having a source terminal electrically connected to a current carrying terminal of the third lateral ground select transistor.
7. The memory device of claim 6 , wherein a net conductivity type of a channel region of the third lateral ground select transistor is of first conductivity type.
8. The memory device of claim 6 , wherein a channel region of the third lateral ground select transistor comprises a region of first conductivity type.
9. The memory device of claim 6 , wherein a channel region of the third lateral ground select transistor comprises a region of first conductivity type and a region of second conductivity type.
10. The memory device of claim 6 , further comprising vertical channels vertically provided from a substrate channel region on the substrate between the first and second common source lines, wherein the vertical channels are coupled to the NAND-type strings, and wherein the vertical channels that are just adjacent to each other are alternately offset to each other.
11. The memory device of claim 10 , wherein two selection lines are provided between the first and second common source lines.
12. The memory device of claim 6 , further comprising vertical channels vertically provided from a substrate channel region on the substrate between the first and second common source lines, wherein the vertical channels are coupled to the NAND-type strings, and wherein the vertical channels that are just adjacent to each other are alternately offset to each other and comprise a first channel, a second channel which is offset from the first channel, a third channel which is offset from the first and second channels, and a fourth channel which is aligned with the first channel in a first direction.
13. The memory device of claim 12 , wherein one selection line is provided between the first and second common source lines.
14. A nonvolatile memory device comprising:
a plurality of common source lines provided in a substrate, and extended in a first direction to be separated from each other; and
a plurality of transistors provided between the common source lines, and using the substrate as a channel,
wherein the transistors comprise:
a plurality of first transistors separated by a first distance from the common source lines, and having a first threshold voltage; and
a plurality of second transistors separated by a second distance greater than the first distance from the common source lines, and having a second threshold voltage different from the first threshold voltage.
15. The nonvolatile memory device of claim 14 , wherein the first threshold voltage is greater than the second threshold voltage.
16. The nonvolatile memory device of claim 15 , further comprising:
a plurality of vertical channels vertically provided from the substrate between the common source lines;
a plurality of conductive patterns stacked on the substrate to be separated from each other, wherein the vertical channels pass through the conductive patterns; and
an information storage layer provided between the vertical channels and the conductive patterns,
wherein a lowermost conductive pattern serves as gates of the transistors.
17. The nonvolatile memory device of claim 16 , wherein the vertical channels are provided between the first transistors and the second transistors, or between the second transistors.