Integrated circuit including U-shaped access device

1. An integrated circuit comprising:

a U-shaped access device;

a first line coupled to a first side of the access device;

a contact coupled to a second side of the access device; and

self-aligned dielectric material isolating the first line from the contact.

2. The integrated circuit of claim 1 , wherein the access device is provided in a substrate, the access device comprising:

a doped first region having a first polarity;

a doped second region having a second polarity opposite the first polarity, the second region isolated from the first region by the dielectric material; and

a doped third region having the first polarity, a top of the third region contacting a bottom of the first region and a bottom of the second region.

3. The integrated circuit of claim 1 , wherein the access device comprises one of a diode and a bipolar transistor.

4. The integrated circuit of claim 1 , further comprising:

a resistance changing memory element, a first side of the memory element coupled to the contact; and

a second line coupled to a second side of the memory element.

5. The integrated circuit of claim 1 , further comprising:

a first silicon layer coupling the first line to the access device.

6. The integrated circuit of claim 2 , wherein the substrate includes a doped fourth region having the second polarity, a top of the fourth region contacting a bottom of the third region.

7. The integrated circuit of claim 2 , wherein the substrate comprises a silicon on insulator structure including an insulating material layer, a top of the insulating material layer contacting a bottom of the third region.

8. The integrated circuit of claim 4 , wherein the memory element and the contact are self-aligned to the second line.

9. The integrated circuit of claim 4 , wherein the memory element comprises a phase change element.

10. The integrated circuit of claim 5 , further comprising:

a second silicon layer coupling the contact to the access device.

11. A system comprising:

a host; and

a memory device communicatively coupled to the host, the memory device comprising:

a U-shaped access device;

a first metal line coupled to a first side of the access device;

a metal contact coupled to a second side of the access device; and

a phase change element, a first side of the phase change element coupled to the metal contact.

12. The system of claim 11 , wherein the access device is provided in a substrate, the access device comprising:

a heavily doped first region having a first polarity;

a heavily doped second region having a second polarity opposite the first polarity, the second region isolated from the first region; and

a lightly doped third region having the first polarity, a top of the third region contacting a bottom of the first region and a bottom of the second region.

13. The system of claim 11 , wherein the access device comprises one of a diode and a bipolar transistor.

14. The system of claim 11 , wherein the memory device further comprises:

a metal bit line coupled to a second side of the phase change element,

wherein the first metal line comprises a word line.

15. The system of claim 14 , wherein the phase change element and the contact are self-aligned to the bit line.

16. A method for fabricating an integrated circuit, the method comprising:

fabricating a U-shaped access device in a substrate;

fabricating a first line coupled to a first side of the access device;

fabricating a contact coupled to a second side of the access device; and

fabricating a resistive memory element having a first side coupled to the contact.

17. The method of claim 16 , wherein fabricating the access device comprises fabricating a diode in a silicon on insulator structure.

18. The method of claim 16 , wherein fabricating the access device comprises fabricating a bipolar transistor in a silicon substrate.

19. The method of claim 16 , further comprising:

fabricating a second line coupled to a second side of the phase change element.

20. The method of claim 16 , wherein fabricating the access device comprises:

providing the substrate including an active area and isolation regions, the active area including a first region having a first polarity;

depositing a doped first silicon layer over the substrate, the first silicon layer having the first polarity;

depositing an electrically conductive material layer over the first silicon layer;

depositing a nitride layer over the electrically conductive material layer;

etching a portion of the nitride layer and the electrically conductive material layer to provide an opening exposing a portion of the first silicon layer;

nitridizing the exposed portion of the first silicon layer to provide a nitridation layer;

damaging a portion of the nitridation layer;

oxidizing the damaged portion of the nitridation layer and the underlying portion of the first silicon layer to provide a first oxide layer;

removing an undamaged portion of the nitridation layer;

depositing a second silicon layer over exposed portions of the first silicon layer, the nitride layer, and the first oxide layer;

depositing a second oxide layer over the second silicon layer in the opening;

etching exposed portions of the second silicon layer and underlying portions of the first silicon layer and the active area to provide a first trench having a first depth and to expose a portion of the first oxide layer;

etching the exposed portion of the first oxide layer and underlying portions of the first silicon layer and the active area to provide a second trench having a second depth less than the first depth;

filling the first trench and the second trench with a dielectric material;

removing the second oxide layer, the second silicon layer, and the first oxide layer to expose a portion of the first silicon layer;

doping the exposed portion of the first silicon layer to provide a doped third silicon layer having a second polarity opposite the first polarity; and

annealing the first and third silicon layers to diffuse dopants into a portion of the first region to provide the access device.

21. The method of claim 16 , wherein fabricating the access device comprises:

providing the substrate including an active area and isolation regions, the active area including a first region having a first polarity;

depositing a doped first silicon layer over the substrate, the first silicon layer having the first polarity;

depositing an electrically conductive material layer over the first silicon layer;

depositing a first nitride layer over the electrically conductive material layer;

etching a portion of the first nitride layer and the electrically conductive material layer to provide an opening exposing a portion of the first silicon layer;

nitridizing the exposed portion of the first silicon layer to provide a nitridation layer;

damaging a portion of the nitridation layer;

oxidizing the damaged portion of the nitridation layer and the underlying portion of the first silicon layer to provide a first oxide layer;

removing an undamaged portion of the nitridation layer;

depositing a second silicon layer over exposed portions of the first silicon layer, the first nitride layer, and the first oxide layer;

depositing a second oxide layer over the second silicon layer in the opening;

etching exposed portions of the second silicon layer and underlying portions of the first silicon layer and the active area to provide a first trench in the substrate having a first depth and to expose a portion of the first oxide layer;

etching the exposed portion of the first oxide layer and underlying portions of the first silicon layer and the active area to provide a second trench in the substrate having a second depth less than the first depth;

filling the first trench and the second trench with a dielectric material;

removing the second oxide layer;

depositing a second nitride layer over exposed portions of the first nitride layer, the dielectric material, the second silicon layer, the first oxide layer, and the first silicon layer;

spacer etching the second nitride layer to expose the second silicon layer;

removing the second silicon layer, the first oxide layer, and the underlying portion of the first silicon layer to expose the substrate;

heavily doping the exposed substrate to provide a doped second region in the substrate having a second polarity opposite the first polarity; and

annealing the first silicon layer to diffuse dopants into the substrate to provide a doped third region in the substrate having the first polarity.

22. The method of claim 20 , wherein damaging the portion of the nitridation layer comprises implanting the portion of the nitridation layer using an angled implantation.

23. The method of claim 20 , wherein fabricating the access device further comprises:

oxidizing exposed portions of the first silicon layer, the second silicon layer, and the active area after etching to provide the second trench.

24. The method of claim 21 , wherein damaging the portion of the nitridation layer comprises implanting the portion of the nitridation layer using an angled implantation.

25. The method of claim 21 , wherein fabricating the access device further comprises:

oxidizing exposed portions of the first silicon layer, the second silicon layer, and the active area after etching to provide the second trench.