Buried metal track and methods forming same

1. An integrated circuit comprising:

a semiconductor substrate;

an isolation region extending into, and overlying a bulk portion of, the semiconductor substrate;

a buried conductive track comprising a portion in the isolation region;

a dielectric layer comprising a bottom portion directly underlying the buried conductive track;

a transistor comprising a source/drain region and a gate electrode, wherein the gate electrode is connected to the buried conductive track; and

a via underlying the gate electrode and connecting the gate electrode to the buried conductive track.

2. The integrated circuit of claim 1 , wherein the buried conductive track comprises a portion extending lower than the transistor.

3. The integrated circuit of claim 1 , wherein the gate electrode is continuously connected to the via, with no interface formed between the gate electrode and the via.

4. The integrated circuit of claim 1 , wherein the dielectric layer comprises:

sidewall portions on opposite sides of the buried conductive track, wherein the sidewall portions have slanted top surfaces, and

the bottom portion is overlapped by the buried conductive track.

5. The integrated circuit of claim 1 , wherein the buried conductive track is physically separated from the transistor.

6. The integrated circuit of claim 1 , wherein the buried conductive track is lower than a top surface of the isolation region.

7. The integrated circuit of claim 1 , wherein the transistor further comprises a gate dielectric underlying the gate electrode, wherein the via penetrates through the gate dielectric.

8. The integrated circuit of claim 1 further comprising:

an additional transistor comprising:

an additional source/drain region over the buried conductive track; and

a source/drain contact plug connecting the additional source/drain region to the buried conductive track.

9. The integrated circuit of claim 8 further comprising an additional via between and connected to the source/drain contact plug and the buried conductive track.

10. An integrated circuit comprising:

a semiconductor substrate comprising a bulk portion;

a dielectric layer comprising:

a bottom portion having a bottom surface contacting a top surface of the bulk portion of the semiconductor substrate; and

sidewall portions over the bottom portion, wherein the sidewall portions are connected to opposite ends of the bottom portion;

a buried metal track over the bottom portion and between the sidewall portions of the dielectric layer;

a dielectric cap overlying and contacting a top surface of the buried metal track;

a shallow trench isolation region extending into the semiconductor substrate;

a semiconductor strip overlying the bulk portion of the semiconductor substrate; and

a semiconductor fin overlapping the semiconductor strip, wherein the semiconductor fin is higher than the shallow trench isolation region, and wherein the buried metal track has a lengthwise direction parallel to a lengthwise direction of the semiconductor fin.

11. The integrated circuit of claim 10 , wherein the bottom portion of the dielectric layer extends into the bulk portion of the semiconductor substrate.

12. The integrated circuit of claim 10 wherein the shallow trench isolation region comprises portions on opposite sides of, and at a same level as, a combined region comprising the buried metal track and the dielectric layer.

13. The integrated circuit of claim 10 further comprising a transistor comprising:

a source/drain region; and

a source/drain contact plug having a first portion overlapping the source/drain region, and a second portion at a same level as the source/drain region, wherein a portion of the buried metal track is overlapped by, and is electrically connected to, the second portion of the source/drain contact plug.

14. The integrated circuit of claim 10 further comprising a transistor comprising:

a gate electrode, wherein the buried metal track is overlapped by, and is electrically connected to, the gate electrode.

15. The integrated circuit of claim 14 , wherein the transistor further comprises a gate dielectric, wherein the buried metal track is connected to the gate electrode through an opening in the gate dielectric.

16. A method comprising:

etching a semiconductor substrate to form a first trench;

filling a metal track into the first trench;

forming a dielectric cap covering the metal track; and

forming a transistor adjacent to the metal track, wherein the transistor comprising:

a source/drain region;

a source/drain contact plug; and

a gate electrode, wherein the metal track comprises a portion overlapped by one of the source/drain contact plug and the gate electrode, wherein the portion of the metal track is underlying and connected to the source/drain contact plug through a via, wherein the via penetrates through the dielectric cap, wherein the via and the gate electrode are formed in a common process.

17. The method of claim 16 , wherein the portion of the metal track is underlying and connected to the gate electrode through a via.

18. The method of claim 16 further comprising forming a shallow trench isolation region comprising portions on opposite sides of the metal track.

19. The method of claim 16 further comprising:

forming a Contact Etch Stop Layer (CESL) and an Inter-Layer Dielectric (ILD) to cover the source/drain region;

etching the ILD and the CESL for form an opening in the ILD and the CESL; and

etching a portion of the dielectric cap to extend the opening into the dielectric cap and to reveal the metal track, wherein the via and the source/drain contact plug are both formed in the opening.

20. The method of claim 19 , wherein the etching the ILD and the CESL and the etching the portion of the dielectric cap are performed using a same etching mask.