Memory cells having storage elements that share material layers with steering elements and methods of forming the same

1. A memory cell comprising:

a storage element formed from a metal-insulator-metal (MIM) stack including:

a first conductive layer;

a reversible resistivity switching (RRS) layer formed above the first conductive layer; and

a second conductive layer formed above the RRS layer, at least one of the first and second conductive layers comprising a first semiconductor material layer; and

a steering element coupled to the storage element, the steering element formed from the first semiconductor material layer of the MIM stack and one or more additional material layers.

2. The memory cell of claim 1 wherein the first semiconductor material layer comprises n-type semiconductor material.

3. The memory cell of claim 2 wherein the first semiconductor material layer comprises n-type silicon.

4. The memory cell of claim 2 wherein the one or more additional material layers comprise undoped semiconductor material and p-type semiconductor material.

5. The memory cell of claim 2 wherein the one or more additional material layers comprise p-type semiconductor material and n-type semiconductor material.

6. The memory cell of claim 1 wherein the first semiconductor material layer comprises p-type semiconductor material.

7. The memory cell of claim 6 wherein the first semiconductor material layer comprises p-type silicon.

8. The memory cell of claim 6 wherein the one or more additional material layers comprise undoped semiconductor material and n-type semiconductor material.

9. The memory cell of claim 6 wherein the one or more additional material layers comprise n-type semiconductor material and p-type semiconductor material.

10. The memory cell of claim 1 wherein the MIM stack includes a silicide layer formed between the RRS layer and the first semiconductor material layer.

11. The memory cell of claim 10 wherein the silicide layer comprises titanium silicide.

12. The memory cell of claim 11 further comprising a titanium oxide layer formed between the RRS layer and the first semiconductor layer.

13. The memory cell of claim 1 wherein the RRS layer comprises HfO X , ZrO X , NiO X , TiO X , TaO X , NbO X or Al X O Y .

14. The memory cell of claim 1 wherein one of the first and second conductive layers comprises heavily doped semiconductor and the other of the first and second conductive layers comprises metal or metal nitride.

15. The memory cell of claim 14 wherein the metal or metal nitride comprises titanium, titanium nitride, tungsten, tungsten nitride, tantalum or tantalum nitride.

16. The memory cell of claim 1 further comprising a metal/metal-oxide layer stack formed between the first and second conductive layers of the MIM stack.

17. The memory cell of claim 16 wherein the metal/metal-oxide layer stack comprises Ti/TiO X , Zr/ZrO X , Ni/NiO X , Al/Al X O Y , Ta/TaO X , Nb/NbO X , or Hf/HfO X .

18. The memory cell of claim 16 wherein the metal/metal-oxide layer stack includes a metal-oxide layer and a metal layer, the metal-oxide layer positioned adjacent and between the RRS layer and the metal layer.

19. The memory cell of claim 18 wherein the metal layer of the metal/metal-oxide layer stack comprises a plurality of metal-rich regions separated by metal oxide.

20. The memory cell of claim 1 wherein the steering element comprises a vertical polycrystalline diode.

21. The memory cell of claim 1 wherein the steering element comprises a punch through diode or a p-i-n junction diode.

22. A memory cell comprising:

a storage element formed from a metal-insulator-metal (MIM) stack; and

a steering element coupled to the storage element, the storage element and steering element sharing at least one layer,

wherein the MIM stack includes:

a first conductive layer;

a reversible resistivity switching (RRS) layer formed above the first conductive layer; and

a second conductive layer formed above the RRS layer, at least one of the first and second conductive layers comprising a first semiconductor material layer; and

the steering element is formed from the first semiconductor material layer of the MIM stack and one or more additional material layers.

23. The memory cell of claim 22 wherein the first semiconductor material layer comprises n-type semiconductor material.

24. The memory cell of claim 23 wherein the first semiconductor material layer comprises n-type silicon.

25. The memory cell of claim 23 wherein the one or more additional material layers comprise undoped semiconductor material and p-type semiconductor material.

26. The memory cell of claim 23 wherein the one or more additional material layers comprise p-type semiconductor material and n-type semiconductor material.

27. The memory cell of claim 22 wherein the first semiconductor material layer comprises p-type semiconductor material.

28. The memory cell of claim 27 wherein the one or more additional material layers comprise undoped semiconductor material and n-type semiconductor material.

29. The memory cell of claim 27 wherein the one or more additional material layers comprise n-type semiconductor material and p-type semiconductor material.

30. The memory cell of claim 22 wherein the MIM stack includes a silicide layer formed between the RRS layer and the first semiconductor material layer.

31. A method of forming a memory cell comprising:

forming a storage element by:

forming a first conductive layer above a substrate;

forming a reversible resistivity switching (RRS) layer above the first conductive layer; and

forming a second conductive layer above the RRS layer, at least one of the first and second conductive layers comprising a first semiconductor material layer; and

forming a steering element coupled to the storage element, the steering element formed from the first semiconductor material layer of the storage element and one or more additional material layers.

32. The method of claim 31 wherein the first semiconductor material layer comprises n-type semiconductor material.

33. The method of claim 32 wherein the first semiconductor material layer comprises n-type silicon.

34. The method of claim 32 wherein the one or more additional material layers comprise undoped semiconductor material and p-type semiconductor material.

35. The method of claim 32 wherein the one or more additional material layers comprise p-type semiconductor material and n-type semiconductor material.

36. The method of claim 31 wherein the first semiconductor material layer comprises p-type semiconductor material.

37. The method of claim 36 wherein the one or more additional material layers comprise undoped semiconductor material and n-type semiconductor material.

38. The method of claim 36 wherein the one or more additional material layers comprise n-type semiconductor material and p-type semiconductor material.

39. The method of claim 31 wherein forming the MIM stack includes forming a silicide layer between the RRS layer and the first semiconductor material layer.

40. The method of claim 39 wherein the silicide layer comprises titanium silicide.

41. The method of claim 40 further comprising forming a titanium oxide layer between the RRS layer and the first semiconductor layer.

42. The method of claim 31 wherein the RRS layer comprises HfO X , ZrO X , NiO X , TiO X , TaO X , NbO X or Al X O Y .

43. The method of claim 31 wherein one of the first and second conductive layers comprises heavily doped semiconductor and the other of the first and second conductive layers comprises metal or metal nitride.

44. The method of claim 43 wherein the metal nitride comprises titanium, titanium nitride, tungsten, tungsten nitride, tantalum or tantalum nitride.

45. The method of claim 31 further comprising forming a metal/metal-oxide layer stack between the first and second conductive layers of the MIM stack.

46. The method of claim 45 wherein the metal/metal-oxide layer stack comprises Ti/TiO X , Zr/ZrO X , Ni/NiO X , Al/Al X O Y , Ta/TaO X , Nb/NbO X , or Hf/HfO X .

47. The method of claim 45 wherein the metal/metal-oxide layer stack includes a metal-oxide layer and a metal layer, the metal-oxide layer positioned adjacent and between the RRS layer and the metal layer.

48. The method of claim 47 wherein the metal layer of the metal/metal-oxide layer stack comprises a plurality of metal-rich regions separated by metal oxide.

49. The method of claim 31 wherein the steering element comprises a vertical polycrystalline diode.

50. The method of claim 31 wherein the steering element comprises a punch through diode or a p-i-n junction diode.

51. A storage element formed by the method of claim 31 .