Semiconductor trench capacitor structure and manufacturing method thereof

1. A semiconductor structure, comprising:

a semiconductor substrate;

a trench capacitor on the semiconductor substrate and comprising a plurality of capacitor segments extending into the semiconductor substrate and separated from each other by pillar segments, wherein each pillar segment has a T-shape shape, and has two sharp corners at a top portion, and two sidewalls beneath the two sharp corners and perpendicular to the semiconductor substrate; and

a protection dielectric layer disposed between the capacitor segments and the pillar segments and overlying top surfaces of the pillar segments.

2. The semiconductor structure of claim 1 , wherein the protection dielectric layer is disposed in line with the pillar segments.

3. The semiconductor structure of claim 1 , wherein the thickness of the protection dielectric layer is uniform.

4. The semiconductor structure of claim 1 , wherein the thickness of the protection dielectric layer is non-uniform.

5. The semiconductor structure of claim 4 , wherein the thickest thickness of the protection dielectric layer is about twice larger the thinnest thickness of the protection dielectric layer.

6. The semiconductor structure of claim 1 , wherein the protection dielectric layer completely overlies the two sharp corners of the pillar segments.

7. The semiconductor structure of claim 1 , wherein the protection dielectric layer is disposed discontinuously and at least covers the two sharp corners of the pillar segments.

8. The semiconductor structure of claim 1 , wherein each capacitor segment comprises an alternative stack of trench electrode layers and capacitor dielectric layers.

9. The semiconductor structure of claim 8 , wherein the protection dielectric layer has a thickness greater than a half of a thinnest thickness of each of the trench electrode layers.

10. The semiconductor structure of claim 8 , wherein the lowest trench electrode layer is in direct contact with the semiconductor substrate.

11. The semiconductor structure of claim 1 , wherein the sharp corners of the pillar segments extend upwardly.

12. The semiconductor structure of claim 1 , wherein a top surface of the pillar segments are warped at edge portions thereof.

13. A semiconductor structure, comprising:

a semiconductor substrate defining a trench, the trench including a top portion having a top width, a bottom portion having a bottom width, and two sidewalls beneath the top portion and perpendicular to the semiconductor substrate, wherein the top width is less than the bottom width;

a protection dielectric layer overlying a top surface of the semiconductor substrate and the two sidewall surfaces of the trench; and

a trench capacitor disposed over the semiconductor substrate and filling the trench, wherein the trench capacitor comprises:

a first trench electrode layer overlying the semiconductor substrate and lining the trench;

a capacitor dielectric layer overlying the first trench electrode layer and lining the trench over the first trench electrode layer; and

a second trench electrode layer overlying the capacitor dielectric layer and filling the trench over the capacitor dielectric layer,

wherein the protection dielectric layer has a thinnest thickness greater than a thinnest thickness of the first trench electrode layer or the second trench electrode layer, and

wherein the first trench electrode layer is in direct contact with the semiconductor substrate.

14. The semiconductor structure of claim 13 , wherein the protection dielectric layer partially overlies the semiconductor substrate and the trench.

15. The semiconductor structure of claim 13 , wherein the thickness of the protection dielectric layer is uniform.

16. The semiconductor structure of claim 13 , wherein the thickness of the protection dielectric layer is non-uniform.

17. The semiconductor structure of claim 16 , wherein the thickest thickness of the protection dielectric layer is about twice larger the thinnest thickness of the protection dielectric layer.

18. The semiconductor structure of claim 13 , wherein the sharp corners of the pillar segments extend upwardly, and a top surface of the pillar segments are warped at edge portions thereof.

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

providing a semiconductor substrate;

performing an etch into the semiconductor substrate to form a trench, wherein the trench includes a top portion having a top width, a bottom portion having a bottom width, and two sidewalls beneath the top portion and perpendicular to the semiconductor substrate, wherein the top width is less than the bottom width;

forming a protection dielectric layer overlying a top surface of the semiconductor substrate and the two sidewall surfaces of the trench; and

forming a layer stack including at least two trench electrode layers interlaced with a capacitor dielectric layer over the semiconductor substrate and filling the trench;

wherein the protection dielectric layer has a thickness greater than a half of a thinnest thicknesses of the at least two trench electrode layers, and

wherein the lower trench electrode layer is in direct contact with the semiconductor substrate.

20. The method of claim 19 , wherein the thickness of the protection dielectric layer is non-uniform, and a thinnest thickness of the protection dielectric layer is twice greater than the thinnest thickness of the at least two trench electrode layers.