Semiconductor device

1. A semiconductor device comprising:

a semiconductor substrate;

a peripheral device on the semiconductor substrate;

a lower insulating structure on the semiconductor substrate and covering the peripheral device;

a first conductive line on the lower insulating structure;

a memory cell structure on the first conductive line,

the memory cell structure including an information storage material pattern and a selector material pattern on the lower insulating structure in a vertical direction,

the selector material pattern including a first selector material layer having a first width and a second selector material layer having a second width narrower than the first width, the first selector material layer including a first material, the second selector material layer including a second material, and a threshold voltage drift of the second material being higher than a threshold voltage drift of the first material; and

a second conductive line on the memory cell structure.

2. The semiconductor device of claim 1 , wherein the selector material pattern is symmetrical with respect to a central axis between both side surfaces of the selector material pattern.

3. The semiconductor device of claim 1 , wherein

the first selector material layer has a first thickness in the vertical direction, and

the second selector material layer has a second thickness greater than the first thickness in the vertical direction.

4. The semiconductor device of claim 1 , wherein the first selector material layer and the second selector material layer have substantially a same thickness.

5. The semiconductor device of claim 1 , wherein the first selector material layer is on the second selector material layer.

6. The semiconductor device of claim 1 , wherein the second selector material layer is on the first selector material layer.

7. The semiconductor device of claim 1 , wherein

the memory cell structure further includes electrode patterns, and

the electrode patterns include a lower electrode pattern below the selector material pattern, an intermediate electrode pattern between the selector material pattern and the information storage material pattern, and an upper electrode pattern above the information storage material pattern.

8. The semiconductor device of claim 7 , wherein

the first selector material layer is on the second selector material layer,

the first selector material layer is in contact with the intermediate electrode pattern, and

the second selector material layer is in contact with the lower electrode pattern.

9. The semiconductor device of claim 1 , wherein

the memory cell structure further includes electrode patterns, and

the electrode patterns include a lower electrode pattern below the information storage material pattern, an intermediate electrode pattern between the selector material pattern and the information storage material pattern, and an upper electrode pattern above the selector material pattern.

10. The semiconductor device of claim 9 , wherein

the first selector material layer is on the second selector material layer,

the first selector material layer is in contact with the upper electrode pattern, and

the second selector material layer is in contact with the intermediate electrode pattern.

11. The semiconductor device of claim 1 , wherein

the first conductive line is a word line, and

the second conductive line is a bit line.

12. The semiconductor device of claim 1 , wherein

a leakage current value of the second material of the second selector material layer is smaller than a leakage current value of the first material of the first selector material layer.

13. A semiconductor device comprising:

a first conductive line on a semiconductor substrate;

a second conductive line on the first conductive line;

a third conductive line on the second conductive line; and

a plurality of memory cell structures on the semiconductor substrate,

the plurality of memory cell structures including a first memory cell structure and a second memory cell structure,

the first memory cell structure being between the first conductive line and the second conductive line,

the first memory cell structure including a first selector material pattern, a first information storage material pattern, and first electrode patterns overlapping each other in a vertical direction,

the second memory cell structure being between the second conductive line and the third conductive line,

the second memory cell structure including a second selector material pattern, a second information storage material pattern, and second electrode patterns overlapping each other in the vertical direction, and

each of the first selector material pattern and the second selector material patterns including a first selector material layer having a first width and a second selector material layer having a second width narrower than the first width.

14. The semiconductor device of claim 13 , wherein the first selector material pattern and the second selector material pattern are symmetrical with respect to a central axis between both side surfaces of each of the first selector material pattern and the second selector material pattern.

15. The semiconductor device of claim 13 , wherein

the first selector material layer has a first thickness in the vertical direction,

the second selector material layer has a second thickness in the vertical direction, and

the second thickness is greater than the first thickness.

16. The semiconductor device of claim 13 , wherein

the first selector material layer of the first selector material pattern is above the second selector material layer of the first selector material pattern, and

the first selector material layer of the second selector material pattern is below the second selector material layer of the second selector material pattern.

17. The semiconductor device of claim 13 , wherein

the first selector material layer of the first selector material pattern is above the second selector material layer of the first selector material pattern, and

the first selector material layer of the second selector material pattern is above the second selector material layer of the second selector material pattern.

18. The semiconductor device of claim 13 , wherein

the first selector material layer of the first selector material pattern is below the second selector material layer of the first selector material pattern, and

the first selector material layer of the second selector material pattern is below the second selector material layer of the second selector material pattern.

19. A semiconductor device comprising:

a first conductive line;

a second conductive line above the first conductive line; and

a memory cell structure between the first conductive line and the second conductive line,

the memory cell structure including an information storage material pattern and a selector material pattern connected to each other in series in a vertical direction,

the selector material pattern including a first selector material layer directly contacting a second selector material layer, the first selector material layer having a first thickness and the second selector material layer having a second thickness,

the first selector material layer including a first material, and the second selector material layer including a second material having a threshold voltage drift higher than a threshold voltage drift of the first material.

20. The semiconductor device of claim 19 , wherein a width of the second selector material layer is narrower than a width of the first selector material layer.