PIEZOELECTRIC THIN FILM DEVICE

Abstract

An object of the present invention is to provide a piezoelectric thin film device including a single or a plurality of film bulk acoustic resonators wherein a frequency impedance characteristic is unsusceptible to spuriousness.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an oblique view showing a schematic configuration of a film bulk acoustic resonator according to a first embodiment of the present invention;

FIGS. 2A to 2D are views showing patterns of an upper electrode, a lower electrode, and an additional film when seen from above, and cross sections of the film bulk acoustic resonator along cutting-plane lines A-A and B-B of FIG. 1;

FIG. 3 is a view showing patterns of the upper electrode and the additional film;

FIG. 4 is an oblique view showing a schematic configuration of a piezoelectric thin film filter according to a second embodiment of the present invention;

FIGS. 5A and 5B are views showing patterns of an upper electrode, a lower electrode, and additional films, when seen from above;

FIG. 6 is a sectional view of the piezoelectric thin film filter along a cutting-plane line VI-VI of FIG. 4;

FIG. 7 is a sectional view showing a state of cutting an assembly integrating a large number of film bulk acoustic resonators into separate film bulk acoustic resonators;

FIGS. 8A to 8C are views for explaining a method for manufacturing the film bulk acoustic resonator;

FIGS. 9A to 9C are views for explaining the method for manufacturing the film bulk acoustic resonator;

FIG. 10 is a view showing a frequency impedance characteristic of a film bulk acoustic resonator according to Example 1;

FIG. 11 is a view showing a frequency impedance characteristic of a film bulk acoustic resonator according to Example 2;

FIG. 12 is a view showing a frequency impedance characteristic of a film bulk acoustic resonator according to Comparative Example; and

FIG. 13 is a view showing patterns of an upper electrode and an additional film.

Claims

1. A piezoelectric thin film device including a single or a plurality of film bulk acoustic resonators, the piezoelectric thin film device comprising: a piezoelectric thin film;a support for supporting said piezoelectric thin film;electrode films formed on both main surfaces of said piezoelectric thin film and having predetermined patterns; anda first additional film formed outside an excitation region for exciting vibrations on at least one of the main surfaces of said piezoelectric thin film.

2. The piezoelectric thin film device according to claim 1, wherein said first additional film is formed on an outer edge section along an outer periphery of said excitation region.

3. The piezoelectric thin film device according to claim 1, further comprising: a second additional film having a conducting property and formed outside a region having said first additional film formed thereon on the main surface of said piezoelectric thin film having said first additional film formed thereon.

4. The piezoelectric thin film device according to claim 3, wherein said second additional film has a thickness larger than that of said first additional film.

5. The piezoelectric thin film device according to claim 1, wherein thickness vibrations are excited in said excitation region.

6. The piezoelectric thin film device according to claim 1, wherein a piezoelectric material constituting said piezoelectric thin film is lithium niobate; andsaid piezoelectric thin film and said support are bonded to each other via an adhesive layer.

7. The piezoelectric thin film device according to claim 1, wherein a material constituting said first additional film is a metal.

8. The piezoelectric thin film device according to claim 1, wherein a mass per unit area of said first additional film formed as superposed on said electrode film is not less than 0.1% and not more than 20% of a sum of a mass per unit area of said piezoelectric thin film and a mass per unit area of said electrode film in said excitation region.

9. The piezoelectric thin film device according to claim 8, wherein the mass per unit area of said first additional film formed as superposed on said electrode film is not less than 1% and not more than 10% of the sum of the mass per unit area of said piezoelectric thin film and the mass per unit area of said electrode film in said excitation region.

10. The piezoelectric thin film device according to claim 1, wherein a region having said first additional film formed thereon extends inside a region separated from said support and enclosing said excitation region.