Piezoelectric resonator, filter, and duplexer

• US 20050057117A1
• Filed: 09/13/2004
• Published: 03/17/2005
• Est. Priority Date: 09/17/2003
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Nakamura, Hiroyuki, Onishi, Keiji, Nakatsuka, Hiroshi, Yamakawa, Takehiko
• Granted Patent: US 7,259,498 B2
• Time in Patent Office: Days
• US Class Current: 310/311
• CPC Class Codes: H03H 9/02094 of adherence
• CPC Class Codes: H03H 9/02102 of temperature influence cutting angles H03H9/02015
• CPC Class Codes: H03H 9/0211 of reflections
• CPC Class Codes: H03H 9/173 Air-gaps
• CPC Class Codes: H03H 9/174 Membranes
• CPC Class Codes: H03H 9/175 Acoustic mirrors
• CPC Class Codes: H03H 9/585 Stacked Crystal Filters [SCF]
• CPC Class Codes: H03H 9/588 Membranes
• CPC Class Codes: H03H 9/589 Acoustic mirrors

Abstract

A piezoelectric resonator of the present invention is structured such that on a substrate 5 having a cavity 4 formed therein, a lower electrode 3, a piezoelectric body 1, a spurious component control layer 16, and an upper electrode 2 are formed in this order from bottom up. The spurious component control layer 16 is a layer for controlling a spurious frequency, and composed of, for example, a metallic material, a dielectric material, or a piezo electric material. By additionally providing the spurious component control layer 16, it is made possible to cause variation of the spurious frequency due to unwanted variation to become greater than variation in resonance frequency of the main resonance of the piezoelectric resonator. Thus, it is possible to realize a piezoelectric resonator having an admittance frequency response where no spurious component occurs between resonance frequency fr and antiresonance frequency fa.

Claims

1. A piezoelectric resonator vibrating at a predetermined frequency, the resonator comprising:

a piezoelectric body;

an upper electrode formed in a direction of a top surface of the piezoelectric body;

a lower electrode formed in a direction of a bottom surface of the piezoelectric body;

a spurious component control layer formed in order to prevent a spurious component from occurring between a resonance frequency and an antiresonance frequency; and

a substrate on which the piezoelectric body, the upper electrode, the lower electrode, and the spurious component control layer are laminated.

2. A piezoelectric resonator according to claim 1, wherein the spurious component control layer is provided between the upper electrode and the piezoelectric body.

3. A piezoelectric resonator according to claim 1, wherein the spurious component control layer is provided between the piezoelectric body and the lower electrode.

4. A piezoelectric resonator according to claim 1, wherein the spurious component control layer is provided on the top surface of the upper electrode.

5. A piezoelectric resonator according to claim 1, wherein the spurious component control layer is provided between the lower electrode and the substrate.

6. A piezoelectric resonator according to claim 1, wherein the spurious component control layer is provided between the upper electrode and the piezoelectric body and between the piezoelectric body and the lower electrode.

7. A piezoelectric resonator according to claim 1, wherein the spurious component control layer is provided between the piezoelectric body and the lower electrode and between the lower electrode and the substrate.

8. A piezoelectric resonator according to claim 6, wherein the spurious component control layer provided between the upper electrode and the piezoelectric body is composed of a material different from a material of the spurious component control layer provided between the piezoelectric body and the lower electrode.

9. A piezoelectric resonator according to claim 7, wherein the spurious component control layer provided between the piezoelectric body and the lower electrode is composed of a material different from a material of the spurious component control layer provided between the lower electrode and the substrate.

10. A piezoelectric resonator according to claim 1, further comprising:

a second piezoelectric body formed on a top surface of the upper electrode; and

a second upper electrode formed on a top surface of the second piezoelectric body.

11. A piezoelectric resonator according to claim 1, wherein a thickness of the spurious component control layer is set so as to be less than or equal to one-fifth of a thickness of the piezoelectric body.

12. A piezoelectric resonator according to claim 1, wherein the spurious component control layer is composed of a metallic material.

13. A piezoelectric resonator according to claim 1, wherein the spurious component control layer is composed of a dielectric material.

14. A piezoelectric resonator according to claim 1, wherein the spurious component control layer is composed of a piezoelectric material different from the material of the piezoelectric body.

15. A piezoelectric resonator according to claim 1, wherein the substrate has a cavity in a portion covered by the lower electrode, the cavity being formed without penetrating the substrate.

16. A piezoelectric resonator according to claim 1, wherein the substrate has a cavity in a portion covered by the lower electrode, the cavity being formed so as to penetrate the substrate.

17. A piezoelectric resonator according to claim 1, wherein an acoustic mirror is provided between the lower electrode and the substrate, the acoustic mirror being structured by alternately laminating a high acoustic impedance layer and a low acoustic impedance layer.

18. A filter having two or more piezoelectric resonators of claim 1 connected in a ladder form.

19. A duplexer comprising:

a transmission filter having two or more piezoelectric resonators of claim 1 connected in a ladder form;

a reception filter having two or more piezoelectric resonators of claim 1 connected in a ladder form; and

a phase-shift circuit for connecting the transmission filter and the reception filter.