Semiconductor structure having fin structures with different gate lengths and method of fabricating thereof

1. A method of fabricating a semiconductor structure, comprising:

forming a plurality of Fin structures;

doping first dopants at both sides of a first Fin structure of the plurality of Fin structures;

providing a first thermal diffusion operation to the semiconductor structure;

doping second dopants at both sides of a second Fin structure of the plurality of Fin structures; and

providing a second thermal diffusion operation to the semiconductor structure,

wherein a first gate length for the first Fin structure is formed using the first and the second thermal diffusion operations, and wherein a second gate length for the second Fin structure is formed using the second thermal diffusion operation, wherein the first gate length and the second gate length are different, wherein the first dopants and the second dopants are the same type or are different type dopants.

2. The method of fabricating the semiconductor structure of claim 1 , wherein providing the first thermal diffusion operation comprises applying the semiconductor structure to a first temperature that reaches or is above a temperature threshold for a thermal diffusion operation of the semiconductor structure.

3. The method of fabricating the semiconductor structure of claim 2 , wherein providing the first thermal diffusion operation comprises diffusing a first portion of the first dopants into the first Fin structure.

4. The method of fabricating the semiconductor structure of claim 3 , wherein applying the second thermal diffusion operation comprises applying the semiconductor structure to a second temperature that reaches or is above the temperature threshold for the thermal diffusion operation of the semiconductor structure.

5. The method of fabricating the semiconductor structure of claim 4 , wherein applying the second thermal diffusion operation comprises diffusing a second portion of the first dopants into the first Fin structure and diffusing a first portion of the second dopants into the second Fin structure.

6. The method of fabricating the semiconductor structure of claim 5 , wherein a first drain/source region of the first Fin structure is formed using the first and the second portions of the first dopants diffused in the first Fin structure.

7. The method of fabricating the semiconductor structure of claim 6 , wherein a second drain/source region of the second Fin structure is formed using the first portion of the second dopants diffused in the second Fin structure.

8. A method of fabricating a vertical transistor, comprising:

forming a plurality of Fin structures in a semiconductor substrate;

doping first dopants into a top surface of the semiconductor substrate at both sides of a first Fin structure of the plurality of Fin structures;

providing a first thermal diffusion operation to the semiconductor substrate;

doping second dopants into the top surface of the semiconductor substrate at both sides of a second Fin structure of the plurality of Fin structures; and

providing a second thermal diffusion operation to the semiconductor substrate,

wherein a first gate length for the first Fin structure is formed using the first and the second thermal diffusion operations, and wherein a second gate length for the second Fin structure is formed using the second thermal diffusion operation, wherein the first gate length and the second gate length are different, wherein the first dopants and the second dopants are the same type or are different type dopants.

9. The method of fabricating the vertical transistor of claim 8 , wherein providing the first thermal diffusion operation comprises:

applying the semiconductor substrate to a first temperature that reaches or is above a temperature threshold for a thermal diffusion operation of the semiconductor substrate; and

diffusing a first portion of the first dopants into the first Fin structure.

10. The method of fabricating the vertical transistor of claim 8 , wherein providing the second thermal diffusion operation comprises:

applying the semiconductor substrate to a second temperature that reaches or is above a temperature threshold for a thermal diffusion operation of the semiconductor substrate; and

diffusing a first portion of the second dopants into the second Fin structure.

11. The method of fabricating the vertical transistor of claim 10 , wherein a first drain/source region comprises a first portion and a second portion of the first dopants diffused into the first Fin structure, and a second drain/source region comprises a first portion of the second dopants diffused into the second Fin structure.

12. The method of claim 8 , wherein the first dopants and the second dopants are N-type or P-type.

13. The method of claim 8 , further comprising:

doping third dopants into the top surface of the semiconductor substrate at both sides of a third Fin structure of the plurality of Fin structures.

14. The method of claim 13 , further comprising:

providing a third thermal diffusion operation to the semiconductor substrate, wherein a third gate length for the Fin structure is formed using the first, second, and third thermal diffusion operations.

15. The method of claim 8 , wherein the first Fin Structure and the second Fin structure have different lengths.

16. The method of claim 13 , wherein the first Fin Structure, the second Fin structure, and the third Fin structure have different lengths.

17. The method of claim 8 , wherein a bottom drain/source region of the first Fin structure is formed using the first dopants.

18. The method of claim 8 , further comprising:

doping third dopants into a top surface of the first Fin structure to form a top source/drain.

19. The method of claim 8 , further comprising a gate conductor around three sides of the first Fin structure.

20. The method of claim 19 , further comprising: removing a portion of the gate conductor.