Semiconductor device

1 . A semiconductor device, comprising:

an upper pad;

an upper dielectric layer that surrounds the upper pad, the upper dielectric layer extends in a first direction and a second direction that intersects the first direction;

a lower pad in contact with the upper pad and the upper dielectric layer; and

a lower dielectric layer that surrounds the lower pad and contacts the upper pad and the upper dielectric layer, the lower dielectric layer extends in the first direction and the second direction,

wherein the upper pad, the upper dielectric layer, the lower pad, and the lower dielectric layer define an upper space that surrounds a lower portion of the upper pad and a lower space that surrounds an upper portion of the lower pad,

wherein the upper space includes a first pad overlap section that overlaps the lower pad in a third direction that intersects the first direction and the second direction, and a first dielectric layer overlap section that overlaps the lower dielectric layer in the third direction,

wherein the lower pad includes a first protrusion part that protrudes toward the first pad overlap section of the upper space,

wherein the first protrusion part of the lower pad is at a level higher than a level of a bottom surface of the upper dielectric layer in the third direction,

wherein the lower pad includes a first surface in contact with the upper dielectric layer and a second surface in contact with the upper pad, and

wherein the first protrusion part of the lower pad is between the first surface and the second surface of the lower pad.

2 . The semiconductor device of claim 1 , wherein

the lower space includes a second pad overlap section that overlaps the upper pad in the third direction and a second dielectric layer overlap section that overlaps the upper dielectric layer in the third direction,

the upper pad includes a second protrusion part that protrudes toward the second pad overlap section of the lower space, and

the second protrusion part of the upper pad is at a level lower than a level of a top surface of the lower dielectric layer in the third direction.

3 . The semiconductor device of claim 2 , wherein the first pad overlap section of the upper space is between the first surface and the second surface of the lower pad.

4 . The semiconductor device of claim 2 , wherein the first and second surfaces of the lower pad are flat.

5 . The semiconductor device of claim 2 , wherein the first surface of the lower pad is between the first pad overlap section of the upper space and the second dielectric layer overlap section of the lower space.

6 . The semiconductor device of claim 5 , wherein the bottom surface of the upper dielectric layer includes a contact part in contact with the first surface of the lower pad, and

wherein the contact part of the bottom surface of the upper dielectric layer is between the first pad overlap section of the upper space and the second dielectric layer overlap section of the lower space.

7 . The semiconductor device of claim 2 , wherein a width of the first surface of the lower pad in the first direction is less than a width of the second surface of the lower pad in the first direction.

8 . The semiconductor device of claim 1 , wherein the first protrusion part of the lower pad includes an exposed surface that is revealed by the first pad overlap section of the upper space, and

wherein the exposed surface is curved.

9 . The semiconductor device of claim 8 , wherein a level of the exposed surface in the third direction decreases as the exposed surface extends in the first direction.

10 . The semiconductor device of claim 8 , wherein the upper pad includes a curved surface that faces the exposed surface.

11 . A semiconductor device, comprising:

an upper pad;

an upper dielectric layer that surrounds the upper pad, the upper dielectric layer extends in a first direction and a second direction that intersects the first direction;

a lower pad in contact with the upper pad and the upper dielectric layer; and

a lower dielectric layer that surrounds the lower pad and contacts the upper pad and the upper dielectric layer, the lower dielectric layer extends in the first direction and the second direction,

wherein the upper pad, the upper dielectric layer, the lower pad, and the lower dielectric layer define an upper space that surrounds a lower portion of the upper pad and a lower space that surrounds an upper portion of the lower pad,

wherein the upper space includes a first pad overlap section that overlaps the lower pad in a third direction that intersects the first direction and the second direction, and a first dielectric layer overlap section that overlaps the lower dielectric layer in the third direction,

wherein the lower pad includes a first surface in contact with the upper dielectric layer and a second surface in contact with the upper pad,

wherein the first pad overlap section is between the first surface and the second surface of the lower pad,

wherein the first and second surfaces of the lower pad are flat, and

wherein the lower pad further includes a protrusion part that protrudes between the first surface and the second surface of the lower pad.

12 . The semiconductor device of claim 11 , wherein the lower space includes a second pad overlap section that overlaps the upper pad in the third direction and a second dielectric layer overlap section that overlaps the upper dielectric layer in the third direction.

13 . The semiconductor device of claim 12 , wherein

the upper pad includes a third surface in contact with the lower dielectric layer and a fourth surface in contact with the lower pad, and

the second pad overlap section is between the third surface and the fourth surface of the upper pad.

14 . The semiconductor device of claim 13 , wherein the third and fourth surfaces of the upper pad are flat.

15 . The semiconductor device of claim 12 , wherein the first surface of the lower pad is between the first pad overlap section and the second dielectric layer overlap section.

16 . The semiconductor device of claim 12 , wherein a bottom surface of the upper dielectric layer includes a contact part in contact with the first surface of the lower pad, and

wherein the contact part is between the first pad overlap section and the second dielectric layer overlap section.

17 . The semiconductor device of claim 11 , wherein the protrusion part includes an exposed surface that is revealed by the first pad overlap section, and

wherein a level of an uppermost portion of the exposed surface is at a level higher than a level of the first surface and a level of the second surface in the third direction.

18 . A semiconductor device, comprising:

a first substrate that extends in a first direction and a second direction that intersects the first direction;

a second substrate spaced apart from the first substrate and that extends in the first direction and the second direction;

a lower pad electrically connected to the first substrate;

a lower dielectric layer that surrounds the lower pad;

an upper pad electrically connected to the second substrate and in contact with the lower pad and the lower dielectric layer; and

an upper dielectric layer that surrounds the upper pad and contacts the lower pad and the lower dielectric layer,

wherein the upper pad, the upper dielectric layer, the lower pad, and the lower dielectric layer define an upper space that surrounds a lower portion of the upper pad and a lower space that surrounds an upper portion of the lower pad,

wherein the upper space includes a first pad overlap section that overlaps the lower pad in a third direction that intersects the first direction and the second direction, and a first dielectric layer overlap section that overlaps the lower dielectric layer in the third direction,

wherein the lower space includes a second pad overlap section that overlaps the upper pad in the third direction and a second dielectric layer overlap section that overlaps the upper dielectric layer in the third direction,

wherein the lower pad includes a first protrusion part that protrudes toward the first pad overlap section,

wherein the upper pad includes a second protrusion part that protrudes toward the second pad overlap section,

wherein the first protrusion part is at a level higher than a level of a top surface of the lower dielectric layer in the third direction,

wherein the second protrusion part is at a level lower than a level of a bottom surface of the upper dielectric layer in the third direction,

wherein the upper pad includes a first surface in contact with the lower dielectric layer and a second surface in contact with the lower pad, and

wherein the second protrusion part protrudes between the first surface and the second surface of the upper pad.