Integrated circuit and manufacturing method thereof

1. A method, comprising:

depositing a first dielectric layer over a substrate;

depositing a metal layer over the first dielectric layer;

patterning the first dielectric layer and the metal layer;

depositing a second dielectric layer over the metal layer, such that the second dielectric layer is in contact with a top surface of the metal layer, sidewalls of the metal layer, and the sidewalls of the first dielectric layer;

forming a plurality of first vias in the second dielectric layer and in contact with a top surface of the metal layer; and

forming a transistor over the second dielectric layer and in contact with at least one of the plurality of first vias.

2. The method of claim 1 , wherein depositing the second dielectric layer is performed such that the second dielectric layer is in contact with the substrate.

3. The method of claim 1 , further comprising:

forming second vias in the second dielectric layer and in contact with a top surface of the metal layer, wherein the second vias surrounding the first vias;

forming an interlayer dielectric layer surrounding the integrated circuit; and

forming interconnection structures in the interlayer dielectric layer and in contact with the second vias.

4. The method of claim 3 , wherein the first vias and the second vias are formed at the same time.

5. A method, comprising:

forming a first dielectric layer over a front side of a substrate;

forming a plurality of first vias extending through the first dielectric layer and into the substrate;

forming a transistor over the first dielectric layer;

etching a backside of the substrate to form a recessed region in the backside of the substrate;

forming a plurality of second vias through the recessed region of the substrate, such that the second vias are in contact with the first vias; and

depositing a metal layer in the recessed region in the backside of the substrate and in contact with the second vias.

6. The method of claim 5 , further comprising:

after forming the first dielectric layer, etching the first dielectric layer and the substrate to form recesses; and

filling a dielectric material in the recesses.

7. The method of claim 5 , wherein forming the second vias is performed such that each of the second vias is in contact with at least two of the first vias.

8. The method of claim 5 , wherein forming the second vias is performed such that the second vias is wider than the first vias.

9. The method of claim 5 , further comprising forming a second dielectric layer over the backside of the substrate and covering the metal layer.

10. The method of claim 5 , wherein prior to etching the backside of the substrate, further comprising:

forming a redistribution layer over the transistor;

forming a plurality of bumps over the redistribution layer;

forming a carrier covering the bumps; and

flipping over the substrate.

11. A method, comprising:

forming a first power line over a substrate;

forming an integrated circuit over the first power line, the first power line being vertically between the substrate and the integrated circuit, wherein the integrated circuit comprises:

a first transistor having a first active region and a first gate structure wrapping around the first active region on four sides of the first active region, wherein the first active region has a source region and a drain region on opposite sides of the first gate structure, wherein the first power line is electrically connected to the source region of first active region of the first transistor;

a second transistor vertically above the first transistor, and having a second active region and a second gate structure wrapping around the second active region on four sides of the second active region, wherein the second active region has a source region and a drain region on opposite sides of the second gate structure; and

a second power line vertically above second transistor, wherein the second power line is electrically connected to the source region of second active region of the second transistor.

12. The method of claim 11 , further comprising forming a dielectric layer over the substrate prior to forming the first power line.

13. The method of claim 12 , wherein further comprising patterning the dielectric layer and the first power line prior to forming the integrated circuit.

14. The method of claim 11 , further comprising:

forming a dielectric layer over the first power line; and

forming a conductive via in the dielectric layer and electrically connected to the first power line.

15. The method of claim 11 , further comprising:

forming an interlayer dielectric layer surrounding the integrated circuit; and

forming interconnection structures in the interlayer dielectric layer and electrically connected to the first power line.

16. The method of claim 15 , further comprising forming vias over the first power line prior to forming the integrated circuit, wherein the interconnection structures are electrically connected to the first power line through the vias.

17. The method of claim 11 , wherein the first power line vertically overlaps the second power line.

18. The method of claim 11 , wherein an area of the first power line is greater than an area of the second power line.

19. The method of claim 11 , wherein the integrated circuit further comprises a via between the first transistor and the second transistor, the via electrically connecting the first gate structure of the first transistor to the second gate structure of the second transistor.

20. The method of claim 11 , wherein the first transistor and the second transistor have different conductivity types.