Semiconductor structure
A semiconductor structure is provided. The semiconductor structure includes a first nanowire over a semiconductor fin. The semiconductor structure also includes a second nanowire over the first nanowire and a third nanowire over the second nanowire. The semiconductor structure further includes a source/drain wrapping around the first nanowire, the second nanowire and the third nanowire. A thickness of a first portion of the source/drain vertically sandwiched between the first nanowire and the second nanowire is different from a thickness of a second portion of the source/drain vertically sandwiched between the second nanowire and the third nanowire.
1. A semiconductor structure, comprising:
a first nanowire over a semiconductor fin;
a second nanowire over the first nanowire;
a third nanowire over the second nanowire; and
a source/drain wrapping around the first nanowire, the second nanowire and the third nanowire, wherein a thickness of a first portion of the source/drain vertically sandwiched between the first nanowire and the second nanowire is different from a thickness of a second portion of the source/drain vertically sandwiched between the second nanowire and the third nanowire.
2. The semiconductor structure of claim 1 , wherein the first portion of the source/drain is in direct contact with the first nanowire and the second nanowire.
3. The semiconductor structure of claim 2 , wherein the second portion of the source/drain is in direct contact with the second nanowire and the third nanowire.
4. The semiconductor structure of claim 1 , further comprising:
an isolation structure surrounding the semiconductor fin.
5. The semiconductor structure of claim 4 , wherein a top surface of the semiconductor fin is lower than a top surface of the isolation structure.
6. The semiconductor structure of claim 4 , wherein a top surface of the semiconductor fin is higher than a top surface of the isolation structure.
7. The semiconductor structure of claim 1 , wherein the thickness of the first portion of the source/drain is greater than the thickness of the second portion of the source/drain by a range of from about 0.5 nm to about 1.5 nm.
8. The semiconductor structure of claim 1 , further comprising:
a fourth nanowire over the third nanowire wrapped around by the source/drain, wherein the thickness of the second portion of the source/drain vertically sandwiched between the second nanowire and the third nanowire is different from a thickness of a third portion of the source/drain vertically sandwiched between the third nanowire and the fourth nanowire.
9. A semiconductor structure, comprising:
a first nanowire;
a second nanowire over the first nanowire;
a third nanowire over the second nanowire; and
a first gate wrapping around the first nanowire, the second nanowire and the third nanowire, wherein a thickness of a first portion of the first gate between the first nanowire and the second nanowire is different from a thickness of a second portion of the first gate between the second nanowire and the third nanowire.
10. The semiconductor structure of claim 9 , further comprising:
a first semiconductor fin below the first nanowire; and
an isolation structure surrounding the first semiconductor fin.
11. The semiconductor structure of claim 10 , wherein a top surface of the first semiconductor fin is lower than a top surface of the isolation structure.
12. The semiconductor structure of claim 10 , wherein a top surface of the first semiconductor fin is higher than a top surface of the isolation structure.
13. The semiconductor structure of claim 10 , further comprising:
a second semiconductor fin;
a fourth nanowire, a fifth nanowire and a sixth nanowire over the second semiconductor fin; and
a second gate wrapping around the fourth nanowire, the fifth nanowire and the sixth nanowire.
14. The semiconductor structure of claim 13 , wherein a top surface of the second gate is higher than a top surface of the first gate.
15. The semiconductor structure of claim 13 , wherein a top surface of the second semiconductor fin is higher than a top surface of the first semiconductor fin.
16. A semiconductor structure, comprising:
a semiconductor fin on a substrate;
a first channel structure most proximal to a top surface of the semiconductor fin;
a second channel structure second most proximal to the top surface of the semiconductor fin; and
a third channel structure third most proximal to the top surface of the semiconductor fin, wherein a first spacing between the first channel structure and the second channel structure is different from a second spacing between the second channel structure and the third channel structure.
17. The semiconductor structure of claim 16 , wherein thicknesses of the first channel structure, the second channel structure and the third channel structure are identical.
18. The semiconductor structure of claim 16 , further comprising:
an isolation structure surrounding the semiconductor fin.
19. The semiconductor structure of claim 18 , wherein the top surface of the semiconductor fin is lower than a top surface of the isolation structure.
20. The semiconductor structure of claim 18 , wherein a top surface of the first semiconductor fin is higher than the top surface of the isolation structure.