Content addressable memory using threshold-adjustable vertical transistors and methods of forming the same

1. A content addressable memory element comprising:

a vertical transistor comprising:

a gate oxide comprising a ferroelectric material;

a first gate electrode coupled to a first search line; and

a second gate electrode coupled to a second search line,

wherein the first search line and second search line comprise complimentary states.

2. The content addressable memory element of claim 1 , wherein the gate oxide comprises hafnium oxide.

3. The content addressable memory element of claim 1 , wherein the gate oxide comprises hafnium oxide doped with one or more of silicon, aluminum, zirconium, yttrium, gadolinium, calcium, cerium, dysprosium, erbium, germanium, scandium, and tin.

4. The content addressable memory element of claim 1 , wherein the first gate electrode and a second gate electrode are disposed on opposite sides of the vertical transistor.

5. The content addressable memory element of claim 1 , wherein the content addressable memory element comprises the vertical transistor and no other circuit elements.

6. The content addressable memory element of claim 1 , comprising two memory cells.

7. The content addressable memory element of claim 1 , wherein the vertical transistor comprises:

a first electrode coupled to a match line; and

a second electrode coupled to a ground line.

8. The content addressable memory element of claim 1 , wherein the vertical transistor comprises a field effect transistor.

9. The content addressable memory element of claim 1 , wherein the vertical transistor comprises a first region having a first conductivity type, a second region having a second conductivity type above the first region, and a third region having the first conductivity type above the second region.

10. A content addressable memory cell array comprising:

a plurality of match lines disposed in parallel along a first axis;

a plurality of ground lines disposed in parallel along the first axis;

a plurality of search lines disposed in parallel substantially perpendicular to the first axis; and

a plurality of content addressable memory elements, each content addressable memory element comprising a vertical ferroelectric transistor disposed between a corresponding one of the match lines and a corresponding one of the ground lines, and each coupled to a corresponding one of the search lines.

11. The content addressable memory cell array of claim 10 , wherein each of the ground lines are disposed above the match lines, and the vertical ferroelectric transistors are disposed above the match lines.

12. The content addressable memory cell array of claim 10 , wherein each of the match lines are disposed above the ground lines, and the vertical ferroelectric transistors are disposed above the ground lines.

13. The content addressable memory cell array of claim 10 , wherein each of the vertical ferroelectric transistors comprises a gate oxide including hafnium oxide.

14. The content addressable memory cell array of claim 10 , wherein each of the vertical ferroelectric transistors comprises a first gate electrode and a second gate electrode.

15. The content addressable memory cell array of claim 14 , wherein the first gate electrode and a second gate electrode are disposed on opposite sides of the vertical ferroelectric transistor.

16. The content addressable memory cell array of claim 10 , wherein each content addressable memory element comprises the vertical ferroelectric transistor and no other circuit elements.

17. The content addressable memory cell array of claim 10 , wherein each content addressable memory element comprises two memory cells.

18. A three-dimensional content addressable memory cell array comprising:

a first memory level disposed above a substrate, the first memory level comprising:

a plurality of first match lines disposed in parallel along a first axis;

a plurality of first ground lines disposed in parallel along the first axis and above the plurality of first match lines;

a plurality of first search lines disposed in parallel substantially perpendicular to the first axis; and

a plurality of first content addressable memory elements, each first content addressable memory element comprising a vertical ferroelectric transistor disposed between a corresponding one of the first match lines and a corresponding one of the first ground lines, and each coupled to a corresponding one of the first search lines; and

a second memory level disposed above the first memory level, the second memory level comprising:

a plurality of second match lines disposed in parallel along the first axis and above the plurality of first ground lines;

a plurality of second search lines disposed in parallel substantially perpendicular to the first axis; and

a plurality of second content addressable memory elements, each second content addressable memory element comprising a vertical ferroelectric transistor disposed between a corresponding one of the second match lines and a corresponding one of the first ground lines, and each coupled to a corresponding one of the second search lines.

19. The three-dimensional content addressable memory cell array of claim 18 , wherein each of the vertical ferroelectric transistors comprises a gate oxide including hafnium oxide.