Methods of forming semiconductor constructions

1. A method of forming a magnetoresistive memory device, comprising:

forming a memory bit comprising a stack which includes a first magnetic mass, a second magnetic mass, and a non-magnetic mass between the first and second magnetic masses;

forming first, second and third layers over the memory bit, and over a region proximate the memory bit;

removing the second and third layers from over the memory bit, while leaving portions of the second and third layers over the region proximate the memory bit; at least some of the second layer being removed from under the third layer to leaving a channel over the region proximate the memory bit; and

forming a magnetic material within the channel.

2. The method of claim 1 further comprising removing the first layer from over the memory bit.

3. The method of claim 1 wherein the removing the second and third layers from over the memory bit comprises chemical-mechanical polishing of the second and third layers.

4. The method of claim 1 wherein the removing the second and third layers from over the memory bit comprises chemical-mechanical polishing of the second and third layers; and wherein the removal of at least some of the second layer from under the third layer occurs subsequent to the chemical-mechanical polishing and comprises an etch selective for the second layer relative to the third layer.

5. The method of claim 1 wherein the removing the second and third layers from over the memory bit comprises chemical-mechanical polishing of the second and third layers, and wherein the chemical-mechanical polishing also removes the first layer from over the memory bit.

6. The method of claim 1 wherein the first and third layers are identical to one another in composition, and wherein the second layer is different in composition from the first and third layers.

7. The method of claim 1 wherein the third layer comprises silicon dioxide and the second layer comprises silicon nitride.

8. The method of claim 1 wherein the first and third layers comprise silicon dioxide and the second layer comprises silicon nitride.

9. The method of claim 1 wherein the third layer comprises silicon nitride and the second layer comprises silicon dioxide.

10. The method of claim 1 wherein the first and third layers comprise silicon nitride and the second layer comprises silicon dioxide.

11. The method of claim 1 wherein the first and third layers comprise silicon carbide and the second layer does not comprise silicon carbide.

12. The method of claim 1 wherein the first and third layers consist essentially of one or both of silicon and carbon; and wherein the second layer consists essentially of silicon and oxygen.

13. The method of claim 12 wherein the removing the second and third layers from over the memory bit comprises chemical-mechanical polishing of the second and third layers; and wherein the removal of at least some of the second layer from under the third layer occurs subsequent to the chemical-mechanical polishing and comprises an etch selective for the second layer relative to the third layer, the etch utilizing one or both of ammonium fluoride and hydrofluoric acid.

14. The method of claim 1 wherein the third layer consists essentially of silicon and one or both of nitrogen and oxygen; and wherein the second layer comprises carbon.

15. The method of claim 1 wherein the first and third layers consist essentially of silicon and one or both of nitrogen and oxygen; and wherein the second layer comprises carbon.

16. The method of claim 15 wherein the removing the second and third layers from over the memory bit comprises chemical-mechanical polishing of the second and third layers; and wherein the removal of at least some of the second layer from under the third layer occurs subsequent to the chemical-mechanical polishing and comprises an etch selective for the second layer relative to the third layer, the etch utilizing an O 2 plasma.

17. The method of claim 1 wherein the magnetic material formed within the channel comprises one or more of nickel, iron and copper.

18. The method of claim 1 wherein the magnetic material formed within the channel consists essentially of mu-metal.

19. The method of claim 1 wherein the magnetic material consists essentially of nickel and iron.

20. The method of claim 1 wherein the magnetic material consists essentially of nickel and copper.

21. A method of forming a magnetoresistive memory device, comprising:

forming a memory bit comprising a stack which includes a first magnetic mass, a second magnetic mass, and a non-magnetic mass between the first and second magnetic masses;

forming first, second and third layers over the memory bit, and over a region proximate the memory bit;

removing the second and third layers from over the memory bit, while leaving portions of the second and third layers over the region proximate the memory bit;

etching the second layer with an etch selective for the second layer relative to the third layer to remove at least some of the second layer from under the third layer and thereby form a channel over the region proximate the memory bit;

forming a first material within the channel to only partially fill the channel; and

forming a second material within the partially-filled channel, the second material being a magnetic material.

22. The method of claim 21 wherein the removing the second and third layers from over the memory bit comprises chemical-mechanical polishing of the second and third layers.

23. The method of claim 21 wherein the removing the second and third layers from over the memory bit comprises chemical-mechanical polishing of the second and third layers; and wherein the removal of at least some of the second layer from under the third layer occurs subsequent to the chemical-mechanical polishing and comprises an etch selective for the second layer relative to the third layer.

24. The method of claim 21 wherein the removing the second and third layers from over the memory bit comprises chemical-mechanical polishing of the second and third layers, and wherein the chemical-mechanical polishing also removes the first layer from over the memory bit.

25. The method of claim 21 wherein the first and third layers are identical to one another in composition, and wherein the second layer is different in composition from the first and third layers.

26. The method of claim 21 wherein the first and third layers comprising electrically insulative materials, and wherein the second layer comprises a metal-containing material.

27. The method of claim 21 wherein:

the first and third layers comprising electrically insulative materials;

the second layer comprises a metal-containing material; and

the first material formed within the channel comprises a dielectric material.

28. The method of claim 27 wherein the dielectric material comprises silicon dioxide.

29. The method of claim 27 further comprising forming a conductive line over the memory bit, the conductive line being utilized to impart a magnetic field in the memory bit during writing of information to the memory bit; and wherein the conductive line electrically contacts the magnetic material that is formed within the channel.