Microstructure with an enhanced anchor

1. A method of fabricating a microstructure device, the method comprising:

providing a layered wafer, wherein the wafer includes a silicon handle layer, a buried oxide layer on the handle layer, and a silicon device layer on the buried oxide layer;

forming a top oxide layer on the device layer;

etching the top oxide layer, the device layer, and the buried oxide layer, thereby forming trenches to create an anchor and a microstructure device in the device layer;

forming a thermal oxide layer along sides of the microstructure device to enclose the microstructure device in the buried oxide layer, the top oxide layer and the thermal oxide layer;

forming a poly layer to fill in the trenches and enclose the anchor; and

etching away portions of the buried oxide layer, the top oxide layer and the thermal oxide layer enclosing the microstructure device while the poly layer encloses the anchor.

2. The method of claim 1 , wherein the etching the device layer includes a deep reactive ion etch (DRIE) process.

3. The method of claim 1 , further comprising forming the microstructure device as a microelectromechanical systems (MEMS) device.

4. The method of claim 3 , further comprising forming the MEMS device as a piezoelectric resonator.

5. The method of claim 1 , further comprising forming the anchor to be fully attached to the buried oxide layer on a side of the anchor.

6. The method of claim 1 , further comprising bonding a metal-oxide semiconductor (MOS) wafer to the poly layer after etching away the oxide layers enclosing the microstructure device.

7. The method of claim 1 , further comprising encapsulating the microstructure device in a hermetically sealed package and electrically coupling the microstructure device to a contact on an outside of the package.

8. A method of fabricating a microstructure device, the method comprising:

providing a layered wafer, wherein the wafer includes a handle layer, a buried oxide layer on the handle layer, and a device layer on the buried oxide layer;

depositing a top silicon oxide layer on the device layer;

etching the top silicon oxide layer using a first mask, thereby forming a hard mask from the top silicon oxide layer;

etching the device layer using the hard mask, thereby forming an anchor and a microstructure in the device layer;

etching the top silicon oxide layer using a second mask, leaving the top silicon oxide layer on the microstructure;

etching the buried oxide layer using the second mask;

forming a thermal oxide layer on the wafer;

etching the thermal oxide layer using a third mask, leaving an oxide layer enclosing the microstructure;

forming a poly layer on the wafer;

planarizing poly layer;

etching a portion of the poly layer and a portion of the device layer using a fourth mask, thereby creating a handle; and

etching away the oxide layer enclosing the microstructure, thereby releasing the microstructure.

9. The method of claim 8 , wherein the etching the device layer includes a deep reactive ion etch (DRIE) process.

10. The method of claim 8 , further comprising forming the microstructure as a microelectromechanical systems (MEMS) device.

11. The method of claim 10 , further comprising forming the MEMS device as a piezoelectric resonator.

12. The method of claim 8 , further comprising forming the anchor to be fully attached to the buried oxide layer on a side of the anchor.

13. The method of claim 8 , further comprising bonding a metal-oxide semiconductor (MOS) wafer to the poly layer after etching away the oxide layer enclosing the microstructure.

14. The method of claim 8 , further comprising encapsulating the microstructure in a hermetically sealed package and electrically coupling the microstructure to a contact on an outside of the package.

15. A microstructure device comprising:

a silicon handle layer;

a buried silicon oxide layer formed on the handle layer;

an anchor formed on the buried oxide layer, wherein the buried oxide layer extends along a full length of the anchor;

a poly silicon layer formed over the anchor;

a microstructure suspended over the handle, there being an air gap between the poly silicon layer formed over the anchor and the microstructure; and

a metal-oxide semiconductor (MOS) wafer bonded to the poly layer, thereby enclosing the microstructure.

16. The microstructure device of claim 15 , wherein the air gap is less than approximately 200 nm.

17. The microstructure device of claim 15 , further comprising a piezoelectric layer formed on the microstructure.

18. The microstructure device of claim 15 , further comprising a hermetically sealed package encapsulating the microstructure device in a hermetically sealed package.

19. The microstructure device of claim 18 , further comprising a contact electrically coupling the microstructure device to an outside of the package.

20. The method of claim 1 , further comprising removing the top oxide from a top surface of the anchor prior to forming the thermal oxide layer along sides of the microstructure device to enclose the microstructure device in the buried oxide layer.