MEMS device and manufacturing method thereof

1. A MEMS device, comprising:

an anchor;

a diaphragm structure over the anchor, the diaphragm structure having an opening through the diaphragm structure; and

a sealing film covering at least a portion of the opening,

wherein the sealing film forms a bridge across the opening of the diaphragm structure, wherein the diaphragm structure comprises a piezoelectric layer and the sealing film comprises a dielectric layer.

2. The MEMS device of claim 1 , wherein the sealing film angles towards a sidewall of the opening.

3. The MEMS device of claim 1 , wherein the diaphragm structure has a lower surface adjacent to the anchor, and the sealing film is on the lower surface of the diaphragm.

4. The MEMS device of claim 1 , wherein the diaphragm structure has a lower surface adjacent to the anchor and an upper surface opposite to the lower surface, and the sealing film is on the upper surface of the diaphragm structure.

5. The MEMS device of claim 1 , wherein the sealing film comprises a flexible thin film.

6. The MEMS device of claim 1 , wherein the diaphragm structure further comprises a lower electrode layer and an upper electrode layer sandwiching the piezoelectric layer.

7. The MEMS device of claim 1 , wherein the sealing film partially overlaps the diaphragm structure, and partially exposes the diaphragm structure.

8. A MEMS device, comprising:

an anchor;

a membrane having a stationary end fixed on the anchor, and a movable end opposite to the stationary end and defining an opening through the membrane, the opening having a first sidewall and a second sidewall opposite to the first sidewall;

a sealing film over a surface of the membrane; and

a first electrode stack and a second electrode stack over the membrane, wherein the sealing film is disposed between the first electrode stack and the second electrode stack,

wherein a projection of a portion of the sealing film in a direction normal to the surface of the membrane is between the first sidewall and the second sidewall of the opening, and the sealing film fully seals the opening of the membrane.

9. The MEMS device of claim 8 , further comprising a passivation layer along an upper surface of the membrane, wherein the sealing film is disposed on the passivation layer.

10. The MEMS device of claim 8 , wherein the sealing film is disposed on the surface of the membrane adjacent to the anchor.

11. The MEMS device of claim 8 , wherein the sealing film partially covers the membrane and partially exposes the membrane.

12. A method for manufacturing a MEMS device, comprising:

forming a first electrode stack and a second electrode stack over a substrate;

forming a diaphragm structure over the substrate;

forming an opening between the first electrode stack and the second electrode stack and through the diaphragm structure;

reducing a dimension of the opening; and

forming a sealing film to fully seal the opening.

13. The method of claim 12 , further comprising forming a temporary adhesive layer and a carrier over the diaphragm structure, forming a cavity in the substrate, and removing the temporary adhesive layer and the carrier after forming the cavity in the substrate.

14. The MEMS device of claim 8 , wherein each of first electrode stack and the second electrode stack comprises a lower electrode layer, an upper electrode layer and a piezoelectric layer sandwiched between the lower electrode layer and the upper electrode layer.

15. The MEMS device of claim 8 , wherein the sealing film comprises a dielectric layer.

16. The MEMS device of claim 8 , wherein the sealing film comprise a flexible thin film.

17. The method of claim 13 , wherein the opening is connected to the cavity.

18. The method of claim 13 , wherein the opening is separated from the cavity by the sealing film.

19. The method of claim 12 , wherein each of the first electrode stack and the second electrode stack comprises a lower electrode layer, an upper electrode layer, and a piezoelectric layer between the lower electrode layer and the upper electrode layer.

20. The method of claim 19 , wherein the lower electrode layers of the first electrode stack and the second electrode stacked are separated from the substrate by a dielectric layer.