Semiconductor device and manufacturing method thereof

1. A semiconductor device comprising:

a stack structure;

a channel layer penetrating the stack structure;

a gap fill layer including first, second and third dielectric layers, wherein the first dielectric layer is formed in the channel

layer, the second dielectric layer is formed in the first dielectric layer, a third dielectric layer is interposed between the first dielectric layer and the second dielectric layer, and the third dielectric layer includes a material having a higher etching selectivity than the first and second dielectric layers; and

a pad located over the gap fill layer, the pad including a protrusion portion protruding into the gap fill layer.

2. The semiconductor device of claim 1 , wherein the pad is located on the top of the first to third dielectric layers in the channel layer, and the protrusion portion protrudes into the second dielectric layer.

3. The semiconductor device of claim 1 , wherein the first dielectric layer and the second dielectric layer include an oxide layer, and the third dielectric layer includes a nitride layer.

4. The semiconductor device of claim 1 , wherein an upper surface of the gap fill layer includes a recess.

5. The semiconductor device of claim 4 , wherein the recess has a V shaped cross-section or a wedge-shaped cross-section.

6. The semiconductor device of claim 4 , wherein the recess is partially filled by the protrusion portion.

7. The semiconductor device of claim 4 , wherein the recess is completely filled by the protrusion portion.

8. A semiconductor device comprising:

a stack structure;

a channel layer penetrating the stack structure;

a first dielectric layer formed in the channel layer;

a second dielectric layer formed in the first dielectric layer, wherein the second dielectric layer includes a void;

a third dielectric layer interposed between the first dielectric layer and the second dielectric layer, the third dielectric layer including a material having a higher etching selectivity than the first and second dielectric layers.

9. A semiconductor device comprising:

a stack structure;

a channel layer penetrating the stack structure;

a first dielectric layer formed in the channel layer;

a second dielectric layer formed in the first dielectric layer, wherein an upper surface of the second dielectric layer includes a recess; and

a pad located on the top of the first and second dielectric layers, the pad including a protrusion portion protruding into the recess of the second dielectric layer.

10. The semiconductor device of claim 9 , wherein the protrusion portion of the pad fills in the recess.

11. The semiconductor device of claim 9 , wherein the second dielectric layer includes a void, and the protrusion portion of the pad protrudes into the void.

12. The semiconductor device of claim 9 , further comprising a third dielectric layer interposed between the first dielectric layer and the second dielectric layer, the third dielectric layer including a material having a higher etching selectivity than the first and second dielectric layers.

13. The semiconductor device of claim 12 , wherein the first dielectric layer and the second dielectric layer include an oxide layer, and the third dielectric layer includes a nitride layer.

14. The semiconductor device of claim 9 , wherein the first dielectric layer includes a nitride layer and the second dielectric layer includes an oxide layer.

15. The semiconductor device of claim 9 , wherein the first dielectric layer includes an oxide layer and the second dielectric layer includes a nitride layer.

16. The semiconductor device of claim 9 , wherein the recess has a V shaped cross-section or a wedge-shaped cross-section.

17. The semiconductor device of claim 9 , wherein the recess is partially filled by the protrusion portion.

18. The semiconductor device of claim 9 , wherein the recess is completely filled by the protrusion portion.