Buffered finFET device

1. A transistor device comprising:

a semiconductor substrate;

a buffered vertical fin-shaped structure formed in the semiconductor substrate, the vertical fin-shaped structure including

an upper semiconductor layer including a channel region in between drain and source regions,

a buffer region beneath the upper semiconductor layer, the buffer region having a first doping polarity,

at least part of a well region having a second doping polarity which is opposite to the first doping polarity, and

at least one p-n junction between the buffer region and the well region which at least partially covers a horizontal cross section of the vertical fin-shaped structure; and

a gate stack formed over the channel region of the upper semiconductor layer,

wherein a first layer of the well region is directly above the buffer region, and a second layer of the well region is directly below the buffer region at the base of the buffered vertical fin-shaped structure, such that two p-n junctions are present between the buffer region and the well region.

2. The device of claim 1 , further comprising:

oxide-filled trenches adjacent to the vertical fin-shaped structure.

3. The device of claim 2 , further comprising:

an epitaxially-grown layer on the source and drain regions.

4. The device of claim 3 , further comprising:

gate stack spacers adjacent to the gate stack,

wherein the gate stack spacers electrically isolate a gate electrode of the gate stack from the source and drain regions.

5. The device of claim 1 , wherein the buffer region is directly above the well region such that one p-n junction is between the buffer region and the well region.

6. The device of claim 1 , further comprising:

a well tap which bypasses the buffered vertical fin-shaped structure and electrically connects to the well region.

7. The device of claim 1 , wherein the horizontal cross section of the vertical fin-shaped structure is fully covered by the p-n junction.

8. A method of fabricating a finFET device comprising a buffered vertical fin-shaped structure on a semiconductor substrate, the method comprising:

implanting a well region at least partially within the vertical fin-shaped structure to be a first doping polarity; and

implanting a buffer region in the vertical fin-shaped structure to be a second doping polarity which is opposite to the first doping polarity,

wherein at least one p-n junction is formed between the buffer region and the well region and at least partially covers a horizontal cross section of the vertical fin-shaped structure,

wherein the buffer region is implanted within the well region, such that a first p-n junction is formed between the buffer region and a first layer of the well region, and a second p-n junction is formed between the buffer region and a second layer of the well region.

9. The method of claim 8 , further comprising:

performing a trench etch to form trenches defining side surfaces of the vertical fin-shaped structure; and

filling the trenches with oxide.

10. The method of claim 9 , wherein the trench etch also forms trenches defining side surfaces of a vertical well-tap structure which bypasses the buffered vertical fin-shaped structure and electrically connects to the well region.

11. The method of claim 9 , further comprising:

performing an oxide recess such that the oxide in the trenches is recessed so as to expose an upper semiconductor layer of the vertical fin-shaped structure.

12. The method of claim 11 , further comprising:

forming a gate stack over a channel region of the upper semiconductor layer.

13. The method of claim 12 , further comprising:

forming gate stack spacers adjacent to the gate stack; and

performing selective epitaxial growth on source and drain regions of the upper semiconductor layer.

14. The method of claim 8 , wherein the buffer region is implanted directly above the well region, such that one p-n junction is formed between the buffer region and the well region.

15. The method of claim 8 , wherein implants of the well and buffer regions are such that the horizontal cross section of the vertical fin-shaped structure is fully covered by the at least one p-n junction.

16. An integrated circuit comprising at least one buffered finFET device, the buffered finFET device comprising:

a buffered vertical fin-shaped structure which includes at least

an upper semiconductor layer including a channel region in between drain and source regions,

a buffer region beneath the upper semiconductor layer, the buffer region having a first doping polarity,

at least part of a well region having a second doping polarity which is opposite to the first doping polarity, and

at least one p-n junction between the buffer region and the well region which at least partially covers a horizontal cross section of the vertical fin-shaped structure; and

a gate stack formed over the channel region of the upper semiconductor layer,

wherein a first layer of the well region is directly above the buffer region, and a second layer of the well region is directly below the buffer region at the base of the buffered vertical fin-shaped structure, such that two p-n junctions are present between the buffer region and the well region.

17. The integrated circuit of claim 16 , further comprising:

a well tap which bypasses the buffered vertical fin-shaped structure and electrically connects to the well region.

18. The integrated circuit of claim 16 , wherein the buffered finFET device is part of a static memory cell.

19. The integrated circuit of claim 16 , wherein the buffered finFET device is part of an analog circuit.