ACOUSTIC WAVE RESONATOR AND ACOUSTIC WAVE FILTER USING THE SAME

• US 20110215883A1
• Filed: 03/01/2011
• Published: 09/08/2011
• Est. Priority Date: 03/02/2010
• Status: Active Grant

• Current Assignee: Skyworks Filter Solutions Japan Co., Ltd. (Skyworks Solutions Incorporated)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Nakamura, Hiroyuki, Tsurunari, Tetsuya, FUJIWARA, Joji
• Granted Patent: US 8,487,720 B2
• Time in Patent Office: Days
• US Class Current: 333/195
• CPC Class Codes: H03H 9/02559 of lithium niobate or lithium-tantalate substrates
• CPC Class Codes: H03H 9/02574 of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate
• CPC Class Codes: H03H 9/02834 of temperature influence cut angles H03H9/02543
• CPC Class Codes: H03H 9/64 using surface acoustic waves
• CPC Class Codes: H03H 9/6483 Ladder SAW filters

Abstract

An acoustic wave resonator includes a piezoelectric substrate and first and second comb-shaped electrodes provided on the piezoelectric substrate and interdigitating with each other. The first comb-shaped electrode includes a first busbar and first electrode fingers extending in a direction non-perpendicular to a direction in which the first busbar extends. The second comb-shaped electrode includes a second busbar and second electrode fingers extending from the second busbar and interdigitating with the first electrode fingers at an interdigitating region. This acoustic wave resonator can suppress a spurious response due to a transverse mode and has a high Q value.

Claims

1. An acoustic wave resonator comprising:

a piezoelectric substrate having an upper surface; and

an interdigital transducer (IDT) electrode that includes a first comb-shaped electrode provided on the upper surface of the piezoelectric substrate and a second comb-shaped electrode provided on the upper surface of the piezoelectric substrate, the second comb-shaped electrode interdigitating with the first comb-shaped electrode,

wherein the first comb-shaped electrode includes;

a first busbar provided on the upper surface of the piezoelectric substrate to extend in a first direction; and

a plurality of first electrode fingers that are provided on the upper surface of the piezoelectric substrate and that extend from the first busbar in a second direction non-perpendicular to the first direction,

the second comb-shaped electrode includes;

a second busbar provided on the upper surface of the piezoelectric substrate to extend in the first direction; and

a plurality of second electrode fingers that are provided on the upper surface of the piezoelectric substrate and that extend from the second busbar in a third direction opposite to the second direction, the plurality of second electrode fingers interdigitating with the plurality of first electrode fingers at an interdigitating region.

2. The acoustic wave resonator according to claim 1, further comprising

a dielectric film that is provided on the upper surface of the piezoelectric substrate to cover the IDT electrode at the interdigitating region,

wherein the dielectric film has an edge facing the first busbar, and

wherein the edge of the dielectric film extends straight.

3. The acoustic wave resonator according to claim 2, wherein a surface of the dielectric film inclines with respect to the upper surface of the piezoelectric substrate at the edge of the dielectric film.

4. The acoustic wave resonator according to claim 1, further comprising:

a first reflector that is adjacent to the IDT electrode in the first direction; and

a second reflector that is adjacent to the IDT electrode in a direction opposite to the first direction.

5. The acoustic wave resonator according to claim 1, wherein the piezoelectric substrate is made of lithium niobate.

6. The acoustic wave resonator according to claim 1, wherein the piezoelectric substrate is a −

15°

to +35°

rotation Y-cut X-propagation lithium niobate substrate.

7. An acoustic wave filter comprising

a plurality of acoustic wave resonators coupled to each other,

wherein at least one of the plurality of acoustic wave resonators comprises the acoustic wave resonator according to claim 1.

8. The acoustic wave filter according to claim 7, further comprising

a plurality of reflectors provided at both ends of the plurality of acoustic wave resonators,

wherein the plurality of acoustic wave resonators and the plurality of reflectors are provided on the upper surface of the piezoelectric substrate.

9. The acoustic wave filter according to claim 7, wherein the plurality of acoustic wave resonators are connected in a ladder shape.