PIEZOELECTRIC THIN FILM DEVICE

Abstract

The present invention is directed to preventing characteristic variations and damage caused by a difference in thermal expansion coefficient. A piezoelectric thin film filter, including four film bulk acoustic resonators, has a configuration where a filter section for providing a filter function of the piezoelectric thin film filter is bonded with a flat base substrate mechanically supporting the filter section via an adhesive layer. In manufacturing of the piezoelectric thin film filter, a piezoelectric thin film is obtained by performing removal processing on a piezoelectric substrate that can individually stand up under its own weight, but substrates made of one kind of single crystal material are adopted as the base substrate and the piezoelectric substrate, to make the respective thermal expansion coefficients of the piezoelectric thin film and the base substrate coincident with each other.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a piezoelectric thin film filter seen from the top;

FIG. 2 is a sectional pattern view along a cross section II-II of FIG. 1 seen from the front;

FIG. 3 is a sectional pattern view along a cross section III-III of FIG. 1 seen from the right;

FIG. 4 is a circuit diagram showing an electric connection state of four film bulk acoustic resonators included in the piezoelectric thin film filter;

FIG. 5 is a sectional pattern view of a film bulk acoustic resonator included in a piezoelectric thin film filter;

FIG. 6 is a sectional pattern view of the film bulk acoustic resonator included in the piezoelectric thin film filter;

FIG. 7 is a sectional pattern view showing how an assembly, formed by integrating a large number of piezoelectric thin film filters, is separated into individual piezoelectric thin film filters;

FIG. 8 is a view showing the flow of manufacture of the piezoelectric thin film filter according to Example 1;

FIG. 9 is a view showing the flow of manufacture of the piezoelectric thin film filter according to Example 1;

FIG. 10 is a sectional pattern view for explaining a depression formation process;

FIG. 11 is a sectional pattern view for explaining the depression formation process;

FIG. 12 is a sectional view showing a configuration of a conventional piezoelectric thin film device;

FIG. 13 is a sectional view showing the configuration of the conventional piezoelectric thin film device.

Claims

1. A piezoelectric thin film device including a single or a plurality of film bulk acoustic resonators, comprising: a piezoelectric thin film; anda support for supporting a prescribed member including the piezoelectric thin film,wherein the respective linear thermal expansion coefficients of the piezoelectric thin film and the support coincident with each other at least in a direction parallel to the piezoelectric thin film.

2. The piezoelectric thin film device according to claim 1, wherein same kind of material is used for the piezoelectric thin film and the support.

3. The piezoelectric thin film device according to claim 2, wherein crystal axes of the piezoelectric thin film and the support are uniformly oriented.