Transistor having a high germanium percentage fin channel and a gradient source/drain junction doping profile

1. A method of forming a semiconductor device, the method comprising:

forming a fin channel over a bottom source-or-drain (S/D) region;

wherein the fin channel comprises an upper fin channel region and a lower fin channel region;

wherein the bottom S/D region comprises an upper S/D region and a lower S/D region;

forming a S/D junction at an interface between the lower fin channel region and the upper S/D region; and

applying a doping process configured to drive a first type of dopant into the upper fin channel region;

wherein the doping process also diffuses the first type of dopants into the lower fin channel region, across the S/D junction, and into the upper S/D region.

2. The method of claim 1 , wherein the doping process comprises forming an epitaxially grown semiconductor material on a sidewall of the upper fin channel region.

3. The method of claim 2 , wherein the epitaxially grown semiconductor material comprises a selected percentage of the first type of dopant.

4. The method of claim 3 , wherein the doping process further comprises subjecting the epitaxially grown semiconductor material and the upper fin channel region to an anneal operation.

5. The method of claim 4 , wherein a duration and a temperature of the anneal operation are sufficient to drive the first type of dopant from the epitaxially grown semiconductor material into the upper fin channel region.

6. The method of claim 5 , wherein the duration and the temperature of the anneal operation are sufficient to achieve a selected percentage of the first type of semiconductor material in the upper fin channel region.

7. The method of claim 4 , wherein a duration and a temperature of the anneal operation are sufficient to cause the first type of dopant to diffuse from the upper fin channel region into the lower fin channel region, across the S/D junction, and into the upper S/D region.

8. The method of claim 7 , wherein a percentage of the first type of dopant in the upper S/D region is less than a percentage of the first type of dopant in the lower fin channel region.

9. The method of claim 1 , wherein:

the upper channel fin comprises silicon; and

the first type of dopant comprises germanium.

10. A semiconductor device comprising:

a fin channel formed over a bottom source-or-drain (S/D) region;

wherein the fin channel comprises an upper fin channel region and a lower fin channel region;

wherein the bottom S/D region comprises an upper S/D region and a lower S/D region; and

a S/D junction formed at an interface between the lower fin channel region and the upper S/D region;

wherein the upper fin channel region comprises a first type of dopant;

wherein the lower fin channel region comprises the first type of dopant;

wherein the upper S/D region comprises the first type of dopant;

wherein a percentage of the first type of dopant in the upper fin channel region is greater than a percentage of the first type of dopant in the upper S/D region.

11. The semiconductor device of claim 10 , wherein a percentage of the first type of dopant in the upper fin channel region is greater than a percentage of the first type of dopant in the lower fin channel region.

12. The semiconductor device of claim 11 , wherein a percentage of the first type of dopant in the upper S/D region is less than the percentage of the first type of dopant in the lower fin channel region.

13. The semiconductor device of claim 12 , wherein:

the channel fin comprises silicon; and

the first type of dopant comprises germanium.