JP5860675B2 - Elastic wave device - Google Patents

Description

  The present invention relates to an elastic wave device used as a high-frequency filter for mobile communication devices and the like.

  FIG. 3A is an electrode pattern diagram of a conventional acoustic wave device, and FIG. 3B is a cross-sectional view taken along line C-C ′ in FIG.

  3 (a) and 3 (b), the acoustic wave device 1 includes a comb-like shape composed of a plurality of electrode fingers 5 connected to a common electrode 4 between a pair of reflective electrodes 3 on a piezoelectric substrate 2. An elastic wave resonator is formed by crossing the electrodes 6 with each other.

  As prior art document information relating to the invention of this application, for example, Patent Document 1 is known.

JP 2001-68959 A

  In recent years, with the progress of miniaturization of communication devices and higher density of frequency bands, an elastic wave device with less insertion loss and higher efficiency has been required in order for these communication devices to operate reliably.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide an elastic wave device with low insertion loss and high efficiency.

  In order to achieve the above object, the present invention includes a piezoelectric substrate having a concave elastic wave velocity surface and an acoustic wave resonator having a pair of comb electrodes provided on the surface of the piezoelectric substrate, The pair of comb-shaped electrodes has a pair of opposing common electrodes and a plurality of electrode fingers alternately extending from the respective common electrodes to the other common electrode side, and intersects the region where the electrode fingers intersect When the region connecting the gap between the tip of the electrode finger and the comb-shaped electrode facing the region is defined as a gap region, the height of the surface of the piezoelectric substrate is lower than the height of the surface of the piezoelectric substrate in the intersecting region. As described above, a step is provided in the gap region.

  By having the above configuration, the elastic wave device of the present invention reduces the dissipation of the elastic wave energy on both sides perpendicular to the traveling direction of the elastic wave when confining the resonance energy of the elastic wave in the elastic wave waveguide. Therefore, the insertion loss of the acoustic wave device can be reduced.

The top view and sectional drawing which show the elastic wave apparatus in one embodiment of this invention Enlarged view of the main part of the elastic wave device Plan view and sectional view showing a conventional acoustic wave device

  Hereinafter, a surface acoustic wave device according to an embodiment of the present invention will be described with reference to the drawings.

  1A is a plan view of an acoustic wave device according to an embodiment of the present invention, FIG. 1B is a cross-sectional view taken along line AA ′ in FIG. 1A, and FIG. 1C is FIG. Sectional drawing of the BB 'line in (a) and FIG. 2 are the principal part enlarged views of FIG. 1 (a).

  1 (a) to 1 (c) and FIG. 2, an acoustic wave device 11 has an acoustic wave resonator 13 provided on the surface of a piezoelectric substrate 12 made of a rotating Y-cut X-propagating lithium tantalate single crystal. .

  The acoustic wave resonator 13 is configured by providing a pair of reflective electrodes 14 and a pair of comb-shaped electrodes 15 between the reflective electrodes 14 along the propagation direction of the acoustic waves of the piezoelectric substrate 12.

  The pair of comb-shaped electrodes 15 includes a pair of opposed common electrodes 16 and a plurality of electrode fingers 17 alternately extended from the respective common electrodes 16 to the other common electrode 16 side. They are crossed with each other. A dummy electrode finger 18 extending from the other common electrode 16 is provided in the extending direction of the electrode finger 17 extending from one common electrode 16, and the tip of the electrode finger 17 and the tip of the dummy electrode finger 18 are separated by a gap 19. Facing each other. Both ends of the comb-shaped electrode 15 are connected to the input / output terminal 20.

  In this acoustic wave resonator 13, the region where the electrode fingers 17 intersect each other is the intersecting region 21, the region where the dummy electrode fingers 18 are provided is the dummy region 22, and the region connecting the gap 19 is the gap region 23. .

  In the present invention, the recess 24 is provided on the surface of the piezoelectric substrate 12 where the electrode finger 17 and the dummy electrode finger 18 are not formed from the gap region 23 to the dummy region 22, and the height of the surface of the piezoelectric substrate 12 in the recess 24 is provided. Is lower than the height of the surface of the piezoelectric substrate 12 in the intersecting region 21, and a step 25 is formed on the surface of the piezoelectric substrate 12 in the gap region 23.

  As described above, the step 25 is provided in the gap region 23 that connects the gap 19 between the electrode finger 17 and the dummy electrode finger 18 so that the height of the surface of the piezoelectric substrate 12 ahead of the tip of the electrode finger 17 is lowered. Thus, an effect of reflecting the elastic wave at the end of the intersecting region 21 can be given, and thereby loss due to dissipation of elastic energy on both sides of the elastic wave waveguide can be reduced, and insertion loss is reduced. Thus, the highly efficient elastic wave device 11 can be realized.

  In the present embodiment, the acoustic wave resonator 13 has the dummy electrode fingers 18, but the elastic wave resonator 13 that does not have the dummy electrode fingers 18 has the same effect. That is, in the acoustic wave resonator 13 that does not have the dummy electrode finger 18, the tip of the electrode finger 17 is formed in the gap region 23 that connects the gap 19 between the tip of the intersecting electrode finger 17 and the common electrode 16 facing the tip. By providing the step 25 so that the height of the surface of the piezoelectric substrate 12 on the front side becomes lower, an effect of reflecting the elastic wave at the edge of the intersecting region 21 can be given. Loss due to dissipation of elastic energy on both sides can be reduced, and similarly, an elastic wave device 11 with low insertion loss and high efficiency can be realized.

  Further, as the piezoelectric substrate 12, the one having a concave reverse velocity surface of the elastic wave, such as a rotating Y-cut X-propagating lithium tantalate single crystal, is used, and the height of the surface of the piezoelectric substrate 12 in the dummy region 22 is By making it lower than the height of the surface of the piezoelectric substrate 12 in the intersecting region 21, the effect of confining elastic energy on both sides of the acoustic wave resonator 13 can be enhanced. Thus, the loss of the elastic wave resonator 13 due to the dissipation of elastic energy can be reduced, and the elastic wave device 11 with low insertion loss and high efficiency can be realized.

  In the present embodiment, the acoustic wave resonator 13 is a single-terminal pair of acoustic wave resonators, but even if it is a multimode acoustic wave resonator including a plurality of pairs of comb-shaped electrodes 15, It has the same effect.

  The surface acoustic wave device according to the present invention is useful in a high-frequency filter mainly used in mobile communication equipment.

DESCRIPTION OF SYMBOLS 11 Elastic wave apparatus 12 Piezoelectric substrate 13 Elastic wave resonator 15 Comb electrode 16 Common electrode 17 Electrode finger 18 Dummy electrode finger 19 Gap 21 Intersection region 22 Dummy region 23 Gap region 24 Concave portion 25 Step

Claims (12)

A piezoelectric substrate in which the reverse velocity surface of the elastic wave is concave;
An acoustic wave resonator having a pair of comb-shaped electrodes provided on a surface of the piezoelectric substrate, wherein the pair of comb-shaped electrodes includes a pair of opposing common electrodes and the common electrode to the other common electrode side. An acoustic wave resonator having a plurality of alternately extending electrode fingers;
An intersecting region where the electrode fingers intersect;
A gap region connecting the gap between the tip of the electrode finger and the common electrode facing the electrode finger;
And a step provided in the gap region so that the height of the surface of the piezoelectric substrate is lower than the height of the surface of the piezoelectric substrate in the intersecting region.   2. The acoustic wave device according to claim 1, wherein the pair of comb-shaped electrodes have dummy electrode fingers extending from the other common electrode in the extending direction of the electrode fingers.   3. The acoustic wave device according to claim 2, wherein the height of the surface of the piezoelectric substrate in the dummy region provided with the dummy electrode fingers is lower than the height of the surface of the piezoelectric substrate in the intersecting region. The acoustic wave device according to claim 2 , wherein a surface of the piezoelectric substrate in the gap region includes a recess formed by the step .   The acoustic wave device according to claim 4, wherein the height of the surface of the piezoelectric substrate in the recess is lower than the height of the surface of the piezoelectric substrate in the intersecting region. The elastic wave device according to any one of claims 2 to 5 , wherein a tip of the electrode finger and a tip of the dummy electrode finger face each other with the gap therebetween. The gap region acoustic wave apparatus according to any one claim of 6 claim 1 formed on both sides of the waveguide of the acoustic wave. The elastic wave device according to claim 7 , wherein dissipation of elastic energy is reduced on both sides. The acoustic wave device according to any one of claims 1 to 8 , wherein the piezoelectric substrate is made of a rotating Y-cut X-propagating lithium tantalate single crystal. The elastic wave device according to any one of claims 1 to 9 , wherein both ends of the pair of comb electrodes are connected to an input / output terminal. The acoustic wave resonator acoustic wave apparatus according to any one claim of 10 claims 1 is a multi-mode acoustic wave resonator. The acoustic wave device according to claim 11, wherein the multimode acoustic wave resonator includes a plurality of the pair of comb electrodes.

Images