Three-dimensional semiconductor memory devices

1. A three-dimensional semiconductor memory device, comprising:

a substrate including a cell array region and a connection region;

an electrode structure on the substrate, the electrode structure including a plurality of electrodes stacked on a top surface of the substrate in a vertical direction substantially perpendicular to the top surface of the substrate;

a horizontal gate dielectric layer between the electrode structure and the substrate, the horizontal gate dielectric layer including a first portion and a second portion, the first portion of the horizontal gate dielectric layer on the cell array region of the substrate, the second portion of the horizontal gate dielectric layer on the connection region of the substrate, the second portion thicker than the first portion in the vertical direction, and a bottom surface of the second portion of the horizontal gate dielectric layer is at a lower level than a bottom surface of the first portion of the horizontal gate dielectric layer;

a plurality of first vertical channels on the cell array region of the substrate, the plurality of first vertical channels penetrating the electrode structure and the first portion of the horizontal gate dielectric layer; and

a plurality of second vertical channels on the connection region of the substrate, the plurality of second vertical channels penetrating the electrode structure and the second portion of the horizontal gate dielectric layer,

wherein each vertical channel of the plurality of first vertical channels and the plurality of second vertical channels includes a lower semiconductor pattern and an upper semiconductor pattern on the lower semiconductor pattern,

wherein a top surface of a lowermost electrode of the plurality of electrodes is lower than top surfaces of the lower semiconductor patterns of the plurality of first vertical channels and the plurality of second vertical channels, and

wherein a bottom surface of the lowermost electrode is higher than bottom surfaces of the lower semiconductor patterns of the plurality of first vertical channels and the plurality of second vertical channels.

2. The device of claim 1 , wherein top surfaces of the first and second portions of the horizontal gate dielectric layer are substantially coplanar with each other.

3. The device of claim 1 , further comprising:

a device isolation layer on a peripheral circuit region of the substrate, the device isolation layer defining a peripheral active area,

wherein the bottom surface of the second portion of the horizontal gate dielectric layer is at a higher level than a bottom surface of the device isolation layer.

4. The device of claim 1 , wherein each vertical channel of the plurality of first vertical channels and the plurality of second vertical channels includes

an epitaxial pattern penetrating the lowermost electrode of the plurality of electrodes, the epitaxial pattern connected to the substrate; and

a semiconductor pattern on the epitaxial pattern.

5. The device of claim 4 , wherein top surfaces of the epitaxial patterns of the plurality of second vertical channels are proximate to a bottom surface of the substrate in relation to top surfaces of the epitaxial patterns of the plurality of first vertical channels.

6. The device of claim 4 , wherein the epitaxial patterns of the plurality of second vertical channels have respective lengths that are smaller than respective lengths of the epitaxial patterns of the plurality of first vertical channels.

7. The device of claim 4 , wherein respective bottom surfaces of the plurality of second vertical channels are proximate to the bottom surface of the substrate in relation to respective bottom surfaces of the plurality of first vertical channels.

8. The device of claim 4 , wherein

each first vertical channel of the plurality of first vertical channels has a first width, and

each second vertical channel of the plurality of second vertical channels has a second width, the second width greater than the first width.

9. The device of claim 1 , wherein

the electrode structure has a first staircase structure that descends from the connection region toward a peripheral circuit region of the substrate, and

when viewed in plan, the first staircase structure overlaps the second portion of the horizontal gate dielectric layer in the vertical direction.

10. The device of claim 1 , further comprising:

a first peripheral circuit region including a first gate dielectric layer and a first peripheral gate stack on the first gate dielectric layer; and

a second peripheral circuit region including a second gate dielectric layer and a second peripheral gate stack on the second gate dielectric layer, the second gate dielectric layer thinner than the first gate dielectric layer in the vertical direction,

wherein the first peripheral gate stack is closer than the second peripheral gate stack to the electrode structure, and

wherein a thickness of the second portion of the horizontal gate dielectric layer in the vertical direction is substantially equal to or greater than a thickness of the first gate dielectric layer in the vertical direction.

11. The device of claim 10 , wherein

the electrode structure further includes a plurality of interlayer dielectric layers, each interlayer dielectric layer of the plurality of interlayer dielectric layers between a separate pair of adjacent electrodes of the plurality of electrodes, and

one interlayer dielectric layer of the plurality of interlayer dielectric layers covers the first and second peripheral gate stacks.

12. A three-dimensional semiconductor memory device, comprising:

a substrate including a cell array region, and a connection region;

an electrode structure on the substrate, the electrode structure including a plurality of electrodes stacked on a top surface of the substrate in a vertical direction substantially perpendicular to the top surface of the substrate;

a horizontal gate dielectric layer between the electrode structure and the substrate, the horizontal gate dielectric layer including a first portion and a second portion, the first portion of the horizontal gate dielectric layer on the cell array region of the substrate, the second portion of the horizontal gate dielectric layer on the connection region of the substrate, the second portion thicker than the first portion in the vertical direction;

a first vertical channel penetrating the electrode structure on the cell array region and the first portion of the horizontal gate dielectric layer, the first vertical channel including a first lower channel pattern and a first upper channel pattern connected to the first lower channel pattern; and

a second vertical channel penetrating the electrode structure on the connection region and the second portion of the horizontal gate dielectric layer, the second vertical channel including a second lower channel pattern and a second upper channel pattern connected to the second lower channel pattern,

wherein a lowermost electrode of the plurality of electrodes surrounds the first lower channel pattern and the second lower channel pattern, and

wherein a bottom surface of the second lower channel pattern is positioned at a different level from a bottom surface of the first lower channel pattern and

wherein the bottom surface of the second lower channel pattern is positioned at a lower level than a bottom surface of the second portion of the horizontal gate dielectric layer.

13. The device of claim 12 , wherein the bottom surface of the second portion of the horizontal gate dielectric layer is at a lower level than a bottom surface of the first portion of the horizontal gate dielectric layer.

14. The device of claim 12 , wherein a top surface of the lowermost electrode of the plurality of electrodes is lower than top surfaces of lower semiconductor patterns of the first vertical channel and the second vertical channel.

15. The device of claim 12 , wherein the bottom surface of the second lower channel pattern is higher than the bottom surface of the first lower channel pattern.

16. The device of claim 12 , wherein top surfaces of the first and second portions of the horizontal gate dielectric layer are substantially coplanar with each other.

17. The device of claim 12 , further comprising:

a device isolation layer on a peripheral circuit region of the substrate, the device isolation layer defining a peripheral active region;

a first gate dielectric layer on the peripheral active region and a first peripheral gate stack on the first gate dielectric layer,

wherein a thickness of the second portion of the horizontal gate dielectric layer in the vertical direction is substantially equal to or greater than a thickness of the first gate dielectric layer in the vertical direction.

18. The device of claim 12 , wherein the electrode structure has a first staircase structure on the connection region, and

when viewed in plan, the first staircase structure overlaps the second portion of the horizontal gate dielectric layer in the vertical direction.

19. A three-dimensional semiconductor memory device, comprising:

a substrate including a cell array region, and a connection region;

an electrode structure on the substrate, the electrode structure including a plurality of electrodes stacked on a top surface of the substrate in a vertical direction substantially perpendicular to the top surface of the substrate;

a horizontal gate dielectric layer between the electrode structure and the substrate, the horizontal gate dielectric layer including a first portion and a second portion, the first portion of the horizontal gate dielectric layer on the cell array region of the substrate, the second portion of the horizontal gate dielectric layer on the connection region of the substrate;

a first vertical channel penetrating the electrode structure on the cell array region and the first portion of the horizontal gate dielectric layer, the first vertical channel including a first lower channel pattern and a first upper channel pattern connected to the first lower channel pattern; and

a second vertical channel penetrating the electrode structure on the connection region and the second portion of the horizontal gate dielectric layer, the second vertical channel including a second lower channel pattern and a second upper channel pattern connected to the second lower channel pattern,

wherein a top surface of a lowermost electrode of the plurality of electrodes is lower than top surfaces of the first and second lower channel patterns,

wherein a bottom surface of the lowermost electrode is higher than bottom surfaces of the first and second lower channel patterns,

wherein the first portion of the horizontal gate dielectric layer has a first thickness, the second portion of the horizontal gate dielectric layer has a second thickness greater than the first thickness, and the second lower channel pattern has a third thickness greater than the second thickness in the vertical direction.

20. The device of claim 19 , wherein a bottom surface of the second lower channel pattern is positioned at a different level from a bottom surface of the first lower channel pattern.

21. The device of claim 19 , wherein a bottom surface of the second portion of the horizontal gate dielectric layer is at a lower level than a bottom surface of the portion of the horizontal gate dieletric layer, and

wherein top surfaces of the first and second portions of the horizontal gate dielectric layer are substantially coplanar with each other.