Three-dimensional semiconductor memory devices

1. A three-dimensional (3D) semiconductor memory device comprising:

a horizontal structure on an upper surface of a substrate, the horizontal structure comprising a first horizontal pattern and a second horizontal pattern that are sequentially stacked on the upper surface of the substrate in a vertical direction;

a stack structure comprising a plurality of electrodes stacked on the horizontal structure in the vertical direction;

a vertical pattern extending through the plurality of electrodes and connected to the first horizontal pattern; and

a separation structure intersecting the stack structure and the horizontal structure and protruding into the upper surface of the substrate,

wherein a lowermost electrode of the plurality of electrodes comprises first inner sidewalls that face each other and are spaced apart from each other in a first direction with the separation structure interposed therebetween, and the second horizontal pattern comprises second inner sidewalls that face each other and are spaced apart from each other in the first direction with the separation structure interposed therebetween, and

wherein a maximum distance between the first inner sidewalls in the first direction is less than a maximum distance between the second inner sidewalls in the first direction.

2. The 3D semiconductor memory device of claim 1 , wherein the vertical pattern comprises a plurality of vertical patterns, and the separation structure is between first vertical patterns of the plurality of vertical patterns and second vertical patterns of the plurality of vertical patterns and extends longitudinally in a second direction parallel to the upper surface of the substrate.

3. The 3D semiconductor memory device of claim 1 , wherein the first horizontal pattern comprises third inner sidewalls that face each other and are spaced apart from each other with the separation structure interposed therebetween, and a maximum distance between the third inner sidewalls in the first direction is less than the maximum distance between the second inner sidewalls in the first direction.

4. The 3D semiconductor memory device of claim 1 , wherein the first horizontal pattern comprises third inner sidewalls that face each other and are spaced apart from each other in the first direction with the separation structure interposed therebetween, and

wherein a maximum width of the separation structure in the first direction is greater than a maximum distance between the third inner sidewalls in the first direction.

5. The 3D semiconductor memory device of claim 1 , wherein the separation structure has a maximum width in the first direction at a level lower, in the vertical direction, than a lower surface of the first horizontal pattern.

6. The 3D semiconductor memory device of claim 1 , further comprising:

an insulating layer extending between the separation structure and one of the second inner sidewalls of the second horizontal pattern, wherein the insulating layer covers a portion of an upper surface of the first horizontal pattern.

7. The 3D semiconductor memory device of claim 1 , wherein the substrate includes a recess, and a portion of the separation structure is in the recess, and

wherein a depth of the recess in the vertical direction is greater than a thickness of the first horizontal pattern in the vertical direction.

8. The 3D semiconductor memory device of claim 1 , wherein the first horizontal pattern comprises an upper surface that comprises a first portion facing the second horizontal pattern and a second portion protruding toward the separation structure beyond one of the second inner sidewalls of the second horizontal pattern such that the second horizontal pattern does not overlap the second portion of the upper surface of the first horizontal pattern in the vertical direction.

9. The 3D semiconductor memory device of claim 8 , further comprising an interface layer between the first horizontal pattern and the second horizontal pattern,

wherein the interface layer comprises carbon (C) or a conductive material, and

wherein the interface layer does not overlap the second portion of the upper surface of the first horizontal pattern in the vertical direction.

10. A three-dimensional (3D) semiconductor memory device comprising:

a substrate, an upper surface of the substrate comprising a recess;

a stack structure comprising a plurality of electrodes stacked on the upper surface of the substrate in a vertical direction;

a horizontal structure between the stack structure and the substrate, the horizontal structure comprising a first horizontal pattern and a second horizontal pattern that are sequentially stacked on the upper surface of the substrate in the vertical direction; and

a separation structure intersecting the stack structure and the horizontal structure in a first direction parallel to the upper surface of the substrate, a portion of the separation structure being in the recess of the substrate,

wherein the first horizontal pattern comprises first inner sidewalls that face each other and are spaced apart from each other in a second direction that is perpendicular to the first direction with the separation structure interposed therebetween, and

wherein a maximum width of the recess in the second direction is greater than a maximum distance between the first inner sidewalls in the second direction.

11. The 3D semiconductor memory device of claim 10 , further comprising:

a plurality of vertical patterns extending through the plurality of electrodes and connected to the first horizontal pattern,

wherein the separation structure is between first vertical patterns of the plurality of vertical patterns and second vertical patterns of the plurality of vertical patterns.

12. The 3D semiconductor memory device of claim 10 , wherein the portion of the separation structure in the recess is overlapped in the vertical direction by a lowermost electrode of the plurality of electrodes.

13. The 3D semiconductor memory device of claim 10 , wherein the second horizontal pattern comprises second inner sidewalls that face each other and are spaced apart from each other in the second direction with the separation structure interposed therebetween, and

wherein a maximum distance between the second inner sidewalls in the second direction is greater than the maximum distance between the first inner sidewalls in the second direction.

14. The 3D semiconductor memory device of claim 10 , further comprising:

an interface layer extending between the first horizontal pattern and the second horizontal pattern and including carbon (C).

15. The 3D semiconductor memory device of claim 10 , wherein the first horizontal pattern comprises a lower surface that comprises a first portion facing the substrate and a second portion protruding toward the separation structure beyond a sidewall of the recess.

16. A three-dimensional (3D) semiconductor memory device comprising:

peripheral logic circuits on a lower substrate;

a lower insulating layer on the peripheral logic circuits;

a substrate on the lower insulating layer, an upper surface of the substrate comprising a recess;

a stack structure comprising a plurality of electrodes vertically stacked on the upper surface of the substrate;

a horizontal structure between the stack structure and the substrate, the horizontal structure comprising a first horizontal pattern and a second horizontal pattern that are sequentially stacked on the upper surface of the substrate;

a vertical pattern extending through the plurality of electrodes and connected to the first horizontal pattern;

a separation structure intersecting the stack structure and the horizontal structure in a first direction parallel to the upper surface of the substrate, a portion of the separation structure being in the recess of the substrate;

an interface layer between the first horizontal pattern and the second horizontal pattern; and

a first insulating layer between the substrate and the separation structure in the recess of the substrate,

wherein the interface layer extends on a first portion of an upper surface of the first horizontal pattern, and the first insulating layer extends on a second portion of the upper surface of the first horizontal pattern.

17. The 3D semiconductor memory device of claim 16 , wherein the interface layer extends on a first portion of a lower surface of the first horizontal pattern, and the first insulating layer extends on a second portion of the lower surface of the first horizontal pattern.

18. The 3D semiconductor memory device of claim 16 , wherein the first horizontal pattern comprises first inner sidewalls that face each other with the separation structure interposed therebetween, and

wherein the interface layer is in direct contact with the first insulating layer.

19. The 3D semiconductor memory device of claim 16 , wherein the first horizontal pattern comprises first inner sidewalls facing each other with the separation structure interposed therebetween, and

wherein the interface layer does not cover the first inner sidewalls.

20. The 3D semiconductor memory device of claim 16 , further comprising:

a through-interconnection structure comprising a through-insulating pattern vertically extending through the stack structure and a through-plug vertically extending through the through-insulating pattern so as to be connected to the peripheral logic circuits.