Bulk acoustic resonator and filter including the same

1. A bulk acoustic resonator, comprising:

a substrate comprising an upper surface on which a substrate protection layer is disposed; and

a membrane layer forming a cavity together with the substrate,

wherein a thickness of either one or both of the substrate protection layer and the membrane layer is greater at a center of an active region of the bulk acoustic resonator than at an edge of the active region, and

wherein a thickness deviation of either one or both of the substrate protection layer and the membrane layer is 170 Å or less.

2. The bulk acoustic resonator of claim 1 , further comprising:

a lower electrode disposed on the membrane layer;

a piezoelectric layer configured to partially cover the lower electrode; and

an upper electrode disposed on the piezoelectric layer.

3. The bulk acoustic resonator of claim 2 , wherein the upper electrode comprises a frame portion disposed at the edge of the active region.

4. The bulk acoustic resonator of claim 3 , wherein a ratio of half a width of the active region to the thickness deviation of either one or both of the substrate protection layer and the membrane layer is greater than 0.0150 and less than 0.0200.

5. The bulk acoustic resonator of claim 2 , further comprising:

a passivation layer disposed on portions of the upper and lower electrodes; and

a metal pad formed on other portions of the upper and lower electrodes on which the passivation layer is not formed.

6. The bulk acoustic resonator of claim 1 , wherein either one or both of the substrate protection layer and the membrane layer comprise

a dielectric layer comprising any one or any combination of any two or more of manganese oxide (MgO), zirconium oxide (ZrO 2 ), aluminum nitride (AlN), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO 2 ), aluminum oxide (Al 2 O 3 ), titanium oxide (TiO 2 ), and zinc oxide (ZnO), or

a metal layer comprising any one or any combination of any two or more of aluminum (Al), nickel (Ni), chromium (Cr), platinum (Pt), gallium (Ga), and hafnium (Hf).

7. The bulk acoustic resonator of claim 6 , wherein the membrane layer comprises the dielectric layer, and the substrate protection layer comprises either one of silicon nitride and silicon oxide.

8. The bulk acoustic resonator of claim 6 , wherein the substrate protection layer comprises the dielectric layer, and the membrane layer comprises either one of silicon nitride and silicon oxide.

9. A bulk acoustic resonator, comprising:

a substrate comprising an upper surface on which a substrate protection layer is formed; and

a membrane layer forming a cavity together with the substrate,

wherein a thickness of either one or both of the substrate protection layer and the membrane layer is greater at a center of an active region of the bulk acoustic resonator than at an edge of the active region, and

wherein either one or both of the substrate protection layer and the membrane layer comprise

a dielectric layer comprising any one or any combination of any two or more of manganese oxide (MgO), zirconium oxide (ZrO 2 ), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO 2 ), titanium oxide (TiO 2 ), and zinc oxide (ZnO), or

a metal layer comprising any one or any combination of any two or more of aluminum (Al), nickel (Ni), platinum (Pt), gallium (Ga), and hafnium (Hf).

10. The bulk acoustic resonator of claim 9 , further comprising:

a lower electrode disposed on the membrane layer;

a piezoelectric layer configured to partially cover the lower electrode; and

an upper electrode disposed on the piezoelectric layer.

11. The bulk acoustic resonator of claim 10 , further comprising:

a passivation layer disposed on portions of the upper and lower electrodes; and

a metal pad disposed on other portions of the upper and lower electrodes on which the passivation layer is not formed.

12. The bulk acoustic resonator of claim 11 , wherein a thickness deviation of either one or both of the substrate protection layer and the membrane layer is 170 Å or less.

13. The bulk acoustic resonator of claim 9 , wherein the membrane layer comprises the dielectric layer, and the substrate protection layer comprises either one of silicon nitride and silicon oxide.

14. The bulk acoustic resonator of claim 9 , wherein the substrate protection layer comprises the dielectric layer, and the membrane layer comprises either one of silicon nitride and silicon oxide.

15. The bulk acoustic resonator of claim 9 , wherein a ratio of half a width of the active region of the bulk acoustic resonator to a thickness deviation of either one or both of the substrate protection layer and the membrane layer is greater than 0.0150 and less than 0.0200.

16. A filter, comprising:

bulk acoustic resonators,

wherein each of the bulk acoustic resonators comprises

a substrate comprising an upper surface on which a substrate protection layer is disposed, and

a membrane layer forming a cavity together with the substrate,

wherein a thickness of either one or both of the substrate protection layer and the membrane layer is greater at a center of an active region of the bulk acoustic resonator than at an edge of the active region,

wherein a thickness deviation of either one or both of the substrate protection layer and the membrane layer is 170 Å or less, and

wherein the bulk acoustic resonators are connected to each other in series or in parallel.

17. A bulk acoustic resonator, comprising:

a substrate comprising an upper surface on which a substrate protection layer is disposed; and

a membrane layer forming a cavity together with the substrate,

wherein a ratio of half a width of an active region of the bulk acoustic resonator to a thickness deviation of either one or both of the substrate protection layer and the membrane layer is greater than 0.0150 and less than 0.0200.