JP2022039360A - Elastic wave device, communication apparatus, and method for manufacturing elastic wave device - Google Patents

Abstract

To provide an elastic wave device that can improve characteristics.SOLUTION: An elastic wave device 1 has a piezoelectric material 3, IDT electrodes 7 located on a top face 3a of the piezoelectric material 3, and a polarized electrode 9 located on the top face 3a of the piezoelectric material 3 and connected in parallel with the IDT electrodes 7. The polarized electrode 9 has two counter electrodes 19 opposite to each other with a gap G3. In the piezoelectric material 3, a polarization direction in an area directly below the gap G3 is different from a polarization direction in an area in which the IDT electrodes 7 are arranged.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to an elastic wave device using an elastic wave, a communication device including the elastic wave device, and a method for manufacturing the elastic wave device.

Elastic wave devices that utilize elastic waves are known (for example, Patent Documents 1 to 3 below). The surface acoustic wave is, for example, SAW (Surface Acoustic Wave) or BAW (Bulk Acoustic Wave). The elastic wave device has, for example, a piezoelectric body and an IDT (Interdigital Transducer) electrode located on the upper surface of the piezoelectric body. The IDT electrode has two comb tooth electrodes that mesh with each other.

In Patent Documents 1 and 2, a discharge electrode is connected in parallel with the IDT electrode in order to reduce the probability that a discharge will occur between the two comb tooth electrodes. The discharge electrode has two counter electrodes facing each other via a gap on the upper surface of the piezoelectric body. In Patent Document 3, a capacitor connected in parallel to a plurality of IDT electrodes is provided in order to adjust the characteristics of a resonator composed of the plurality of IDT electrodes.

Japanese Unexamined Patent Publication No. 63-189008 Japanese Unexamined Patent Publication No. 2002-314367 Japanese Unexamined Patent Publication No. 2019-121873

A method for manufacturing elastic wave devices, communication devices, and elastic wave devices that can improve the characteristics is awaited.

The elastic wave device according to one aspect of the present disclosure is located on a piezoelectric body, an IDT electrode located on the upper surface of the piezoelectric body, and an IDT electrode located on the upper surface of the piezoelectric body, and is connected in parallel with the IDT electrode. The polarizing electrode has two counter electrodes facing each other with a gap interposed therebetween, and the piezoelectric body has a polarization direction in a region immediately below the gap. It is different from the polarization direction in the region where the IDT electrode is arranged.

The communication device according to one aspect of the present disclosure includes a filter having the elastic wave device, an antenna connected to the filter, and an integrated circuit element connected to the antenna via the filter. have.

In the method for manufacturing an elastic wave device according to one aspect of the present disclosure, the IDT electrode and the polarization electrode connected in parallel to the IDT electrode are attached to the piezoelectric body whose polarization directions are aligned over the entire surface. After the electrode forming step and the electrode forming step, a temperature change is caused in the piezoelectric body, and a voltage is applied to the two counter electrodes by the electric charge generated by the pyroelectric effect to form a region directly below the gap. It has a polarization step that makes the polarization direction in the above different from the polarization direction in the region where the IDT electrode is arranged.

According to the above configuration, the characteristics can be improved.

It is a top view which shows the structure of the main part of the elastic wave device which concerns on 1st Embodiment. FIG. 3 is a cross-sectional view taken along the line II-II of FIG. 3A is a cross-sectional view taken along the line IIIa-IIIa of FIG. 1, and FIG. 3B is a cross-sectional view taken along the line IIIb-IIIb of FIG. It is a flowchart which shows the outline of the procedure of the manufacturing method of the elastic wave device of FIG. It is a top view explaining the change of the polarization direction in the elastic wave device which concerns on a comparative example. It is a top view schematically showing the structure of the main part of the elastic wave device which concerns on 2nd Embodiment. It is a top view schematically showing the structure of the main part of the elastic wave device which concerns on 3rd Embodiment. FIG. 8A is a diagram schematically showing the characteristics of the resonator including the IDT electrode, and FIG. 8B is a diagram showing an example of the influence of the capacitance of the polarization electrode on the frequency difference. It is a figure which shows the deformation example of the shape of a polarization electrode. It is a circuit diagram which shows typically the structure of the demultiplexer which concerns on embodiment. It is a block diagram which shows the structure of the communication apparatus which concerns on embodiment.

Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings. The figures used in the following description are schematic. Therefore, for example, the dimensional ratios on the drawings do not always match the actual ones.

In the following description of the first embodiment, basically, only the differences from the previously described embodiments will be described. Matters not particularly mentioned may be the same as those of the embodiments described above, or may be inferred from the embodiments described above. Further, for the corresponding configurations among a plurality of embodiments, the same reference numerals may be used even if there are differences.

<First Embodiment>
FIG. 1 is a plan view schematically showing the configuration of a main part of the elastic wave device 1 (hereinafter, may be simply referred to as “device 1”) according to the first embodiment.

In the device 1, any direction may be upward or downward, but in the following, for convenience, an orthogonal coordinate system including the D1 axis, the D2 axis, and the D3 axis is attached to the drawing, and the D3 axis is shown. Terms such as top or bottom may be used with the positive side facing up. The D1 axis is defined to be parallel to the propagation direction of the elastic wave propagating along the upper surface 3a of the piezoelectric body 3, which will be described later, and the D2 axis is defined to be parallel to the upper surface 3a and orthogonal to the D1 axis. The D3 axis is defined to be orthogonal to the top surface 3a.

The device 1 has a piezoelectric body 3 and a conductor layer 5 (shown by hatching) located on the upper surface 3a of the piezoelectric body 3. The conductor layer 5 includes one or more (three in the illustrated example) IDT electrodes 7 and one or more (one in the illustrated example) polarization electrodes 9 connected in parallel to the one or more IDT electrodes 7. Have. The IDT electrode 7 and the polarization electrode 9 are connected by, for example, wiring 21.

The piezoelectric body 3 functions as a medium for propagating elastic waves. The IDT electrode 7 contributes to at least one of the conversion of an electric signal to an elastic wave and the conversion of an elastic wave to an electric signal. This conversion is used to realize operation as a resonator or a filter. The polarization electrode 9 contributes to the improvement of the characteristics related to the above conversion. The elastic wave is, for example, SAW, BAW, elastic boundary wave or surface acoustic wave (however, these elastic waves are not always clearly distinguishable).

The device 1 may have two or more polarization electrodes 9 connected in parallel with each other. However, in the following description, an embodiment in which one polarization electrode 9 is used will be taken as an example.

Although not particularly shown, the device 1 may have a protective film (not shown) that covers the upper surface 3a of the piezoelectric body 3 from above the conductor layer 5. Such a protective film is made of, for example, an insulating material such as SiO ₂ , and has a characteristic (for example, resonance characteristic) related to the IDT electrode 7 due to a reduction in the probability that the conductor layer 5 will corrode and / or a temperature change. Contributes to compensating for changes.

Further, the device 1 may have an additional film that overlaps the upper surface or the lower surface of the IDT electrode 7 and has a shape that basically fits in the IDT electrode 7 in planar fluoroscopy. Such an additional film is made of, for example, an insulating material or a metal material having different acoustic characteristics from the material of the IDT electrode 7, and contributes to improving the reflectance coefficient of elastic waves.

(Conductor layer)
The conductor layer 5 is made of the same material and thickness as a whole, for example, in the range shown in the figure. In other words, the IDT electrode 7, the polarization electrode 9, and the wiring 21 are integrally made of the same material and thickness. The material of the conductor layer 5 is, for example, metal. The metal is, for example, Al or an alloy containing Al as a main component (Al alloy). The Al alloy is, for example, an Al—Cu alloy. The conductor layer 5 may be formed by laminating a plurality of metal layers. The thickness of the conductor layer 5 may be appropriately set according to the electrical characteristics required for the element (for example, a resonator or a filter) configured by the IDT electrode 7. As an example, the thickness of the conductor layer 5 is 50 nm or more and 600 nm or less.

(Each IDT electrode)
Each IDT electrode 7 has a pair of comb tooth electrodes 11. Each comb tooth electrode 11 has, for example, a bus bar 13, a plurality of electrode fingers 15 extending in parallel with each other from the bus bar 13, and a plurality of dummy electrodes 17 protruding from the bus bar 13 between the plurality of electrode fingers 15. There is. The pair of comb tooth electrodes 11 are arranged so that the plurality of electrode fingers 15 mesh with each other (intersect).

The bus bar 13 is formed, for example, in an elongated shape having a substantially constant width and extending linearly in the propagation direction (D1 direction) of elastic waves. The pair of bus bars 13 face each other in a direction (D2 direction) orthogonal to the propagation direction of the elastic wave. The width of the bus bar 13 may change or the bus bar 13 may be inclined with respect to the propagation direction of the elastic wave.

Each electrode finger 15 is formed, for example, in a substantially elongated shape extending linearly in a direction (D2 direction) orthogonal to the propagation direction of elastic waves with a substantially constant width. The width of the electrode finger 15 may be changed. In each comb tooth electrode 11, a plurality of electrode fingers 15 are arranged in the propagation direction of elastic waves. Further, the plurality of electrode fingers 15 of one comb tooth electrode 11 and the plurality of electrode fingers 15 of the other comb tooth electrode 11 are basically arranged alternately. From another viewpoint, the electrode finger 15 of one comb tooth electrode 11 and the electrode finger 15 of the other comb tooth electrode 11 face each other through the gap G1.

The pitch p of the plurality of electrode fingers 15 (for example, the distance between the centers of the two electrode fingers 15 adjacent to each other) is basically constant in the IDT electrode 7. The IDT electrode 7 may have a part peculiar with respect to the pitch p. As peculiar parts, for example, a narrow pitch part where the pitch p is narrower than most (for example, 80% or more), a wide pitch part where the pitch p is wider than most (for example, 80% or more), and a small number of electrode fingers 15 are substantially interleaved. The thinned out part drawn is mentioned.

In the following, the term pitch p refers to the pitch of the portion (most of the plurality of electrode fingers 15) excluding the above-mentioned peculiar portion unless otherwise specified. Further, even in most of the plurality of electrode fingers 15 excluding the peculiar portion, when the pitch is changed, the average value of the pitches of most of the plurality of electrode fingers 15 is used as the value of pitch p. You may use it.

The number of electrode fingers 15 may be appropriately set according to the electrical characteristics required for the element (for example, a resonator or a filter) configured by the IDT electrode 7. Since FIG. 1 is a schematic diagram, the number of electrode fingers 15 is shown to be small. In practice, more electrode fingers 15 may be arranged than shown.

The lengths of the plurality of electrode fingers 15 are, for example, equal to each other. The IDT electrode 7 may be subjected to so-called apodization in which the lengths of the plurality of electrode fingers 15 (intersection width W from another viewpoint) change depending on the position in the propagation direction. The length of the electrode finger 15 may be appropriately set according to the required electrical characteristics and the like.

The widths of the plurality of electrode fingers 15 are, for example, equal to each other. From another viewpoint, the duedy ratio of the electrode fingers 15 (ratio of the width of the electrode fingers 15 to the pitch p) and the distance s1 between the adjacent electrode fingers 15 are, for example, equivalent between the plurality of electrode fingers 15. However, the IDT electrode 7 may have a peculiar portion regarding the width, duty ratio and / or interval s1 of the electrode finger 15. Further, the width, duty ratio and / or interval s1 of the electrode fingers 15 may be changed in most of the parts except the peculiar part.

The width, duty ratio and / or interval s1 of the electrode fingers 15 may be appropriately set according to, for example, the required electrical characteristics and the like. For example, the width of the electrode finger 15 may be, for example, 0.3p or more or 0.4p or more, and may be 0.7p or less or 0.6p or less. The above lower and upper limits may be combined as appropriate. On the flip side of this description, the distance s1 between the electrode fingers 15 adjacent to each other via the gap G1 may be 0.3p or more or 0.4p or more, and 0.7p or less or 0.6p or less. May be. The above lower and upper limits may be combined as appropriate. The pitch p in this paragraph may be that of most of the electrode fingers excluding the above-mentioned peculiar portion, or may be related to the individual electrode fingers 15 or the individual intervals s1. ..

The dummy electrode 17 projects, for example, in a direction orthogonal to the propagation direction of the elastic wave with a substantially constant width. The width is equivalent to, for example, the width of the electrode finger 15. Further, the plurality of dummy electrodes 17 are arranged at the same pitch as the plurality of electrode fingers 15, and the tip of the dummy electrode 17 of one comb tooth electrode 11 is the tip of the electrode finger 15 of the other comb tooth electrode 11. And the gap G2 are opposed to each other. From another viewpoint, the tip of the electrode finger 15 of one comb tooth electrode 11 faces the edge portion of the other comb tooth electrode 11 facing the one comb tooth electrode 11 side via the gap G2. The IDT electrode 7 may not include the dummy electrode 17.

The distance s2 between the electrode finger 15 and the dummy electrode 17 is, for example, equal to each other among the plurality of electrode fingers 15. Of course, the plurality of intervals s2 may be different from each other. The interval s2 may be made as small as possible within a range in which the electrode finger 15 and the dummy electrode 17 are not short-circuited, or the electrical characteristics required for the element (for example, a resonator or a filter) configured by the IDT electrode 7 are taken into consideration. May be set. The interval s2 may be, for example, 0.2p or more, 0.3p or more, or 0.4p or more, and may be 2p or less, 1p or less, 0.7p or less, or 0.6p or less. The above lower and upper limits may be combined as appropriate.

When a voltage (a signal from another viewpoint) is applied to the pair of comb tooth electrodes 11, a voltage is applied to the upper surface 3a of the piezoelectric body 3 by the plurality of electrode fingers 15, and the upper surface 3a vibrates. As a result, elastic waves propagating along the upper surface 3a are excited. At this time, the plurality of elastic waves excited by the plurality of electrode fingers 15 are in phase with each other in the direction orthogonal to the plurality of electrode fingers 15 (D1 direction) when the half wavelength thereof is substantially equivalent to the pitch p. The amplitudes are added together. That is, the elastic wave propagating in the D1 direction with the pitch p as a half wavelength is most likely to be excited. As a result, of the voltage applied to the pair of comb tooth electrodes 11, a component having a frequency substantially equal to that of an elastic wave having a pitch p as a half wavelength is converted into an elastic wave. Further, when an elastic wave is generated in the arrangement region of the pair of comb tooth electrodes 11 on the upper surface 3a of the piezoelectric body 3, the pitch p is mainly set to a half wavelength by the opposite principle to the above, and the pitch p is mainly set to a half wavelength in the D1 direction. The elastic wave propagating in is converted into a voltage. A resonator or a filter is realized by utilizing such a principle.

The IDT electrode 7 may be used in various embodiments. For example, the IDT electrode 7 may form a 1-port resonator 37 (FIG. 10) described later by arranging a reflector 31 (FIG. 6) described later in the D1 direction. Further, the IDT electrode 7 is adjacent to one or more other IDT electrodes 7 in the D1 direction, and reflectors are arranged on both sides of the plurality of IDT electrodes 7 to form a vertically coupled multiple mode filter 39 (described later). FIG. 10. It is assumed that a double mode type filter is included.). Further, the IDT electrode 7 may be arranged at a distance from another IDT electrode 7 in the D1 direction to form a transversal type filter (not shown).

(Multiple IDT electrodes)
The plurality of IDT electrodes 7 are connected in series with each other. Note that the connection of the IDT electrodes 7 means a connection in which a voltage is applied to the pair of comb tooth electrodes 11 unless otherwise specified. Therefore, when a plurality of IDT electrodes 7 are connected in series with each other, for example, a first terminal (not shown) and one comb tooth electrode 11 of the first IDT electrode 7 are connected and the first. The other comb tooth electrode 11 of the IDT electrode 7 and one comb tooth electrode 11 of the second IDT electrode 7 are connected, and the other comb tooth electrode 11 of the second IDT electrode 7 and the third IDT It refers to a connection mode in which one comb tooth electrode 11 of the electrode 7 or a second terminal (or a reference potential portion) (not shown) is connected.

More specifically, in the illustrated example, the plurality of IDT electrodes 7 are arranged in a row in the D2 direction, and are connected in series to each other by sharing the bus bar 13 between the adjacent IDT electrodes 7. There is. However, unlike the illustrated example, the plurality of IDT electrodes 7 may be connected to each other by wiring, or may not be arranged in a row in the D2 direction. Further, the illustrated example may be regarded as an embodiment in which wiring having the same width as the length of the bus bar 13 is provided between the bus bars 13 that are not supplied.

The purpose of connecting the plurality of IDT electrodes 7 in series to each other may be various purposes. In other words, the plurality of IDT electrodes 7 connected in series with each other may constitute elastic wave elements of various embodiments.

For example, the plurality of IDT electrodes 7 may be a division of one IDT electrode 7. In this case, the voltage applied to the original one IDT electrode 7 is divided and applied to the plurality of IDT electrodes 7. As a result, the power resistance is improved. In this embodiment, the configurations (dimensions, materials, etc.) of the plurality of IDT electrodes 7 may be, for example, the same as each other.

Further, for example, the plurality of IDT electrodes 7 may constitute a plurality of series resonators 37S (FIG. 10) of a ladder type filter described later. In this embodiment, the plurality of IDT electrodes 7 are configured such that, for example, the resonance frequencies substantially match each other and the antiresonance frequencies substantially match each other. The configurations (dimensions, materials, etc.) of the plurality of IDT electrodes 7 may be the same as each other or may be different from each other.

Further, for example, the plurality of IDT electrodes 7 may constitute a transversely coupled multiple mode type filter. In this case, the filter is configured by acoustically coupling a plurality of (generally two) IDT electrodes 7 to each other. In this embodiment, the configurations (dimensions, materials, etc.) of the plurality of IDT electrodes 7 may be, for example, the same as each other.

(Polarization electrode)
The polarization electrode 9 has a pair of counter electrodes 19 facing each other via the gap G3.

In FIG. 1, the gap G3 is designated at the position where the distance s3 between the pair of counter electrodes 19 is the narrowest. In the following description, the term gap G3 may refer to the entire gap between a pair of counter electrodes 19 and may also refer to a gap at a particular position (eg, where the spacing s3 is the narrowest). Similarly, the interval s3 may refer to the interval of the entire gap and may refer to the interval of the gap at a specific position (eg, the narrowest interval). The same applies to the above-mentioned gaps G1 and G2, and the intervals s1 and s2.

In the description of the dimensions of the polarization electrode 9 and the gap G3 and the like, these dimensions may be compared with the dimensions of the electrode finger 15, the gaps G1 and G2 and the like. The dimensions of the electrode finger 15 and the like at this time may be the dimensions of the electrode finger 15 and the like in most of the parts excluding the peculiar part, or the dimensions of the electrode finger 15 and the like in the peculiar part (minimum value from another viewpoint). Or the maximum value).

The shape of the counter electrode 19 may be appropriately set. In the illustrated example, the counter electrode 19 has a base 19a and one or more (two in the illustrated example) protrusions 19b protruding from the base 19a. The two facing electrodes 19 have the tip of the protruding portion 19b of one facing electrode 19 and the tip of the protruding portion 19b of the other facing electrode 19 facing each other via the gap G3. The gap G3 between the tips is the narrowest gap between the pair of counter electrodes 19. The distance s3 between the tips may be the same for the plurality of protrusions 19b (example in the figure), or may be different from each other.

The shape of the base 19a may be appropriately set. For example, the base 19a may have a rectangular shape (illustrated example), a quadrangular shape other than a rectangular shape, a polygonal shape other than the rectangular shape, a circular shape, or an elliptical shape. At the base 19a, the length (for example, the maximum length) of the two facing electrodes 19 in the facing direction (for example, the D2 direction in the illustrated example) and the length in the direction orthogonal to the facing direction (for example, the maximum length) are the same. It may be (illustrated example), or one may be longer than the other.

The shape of the protrusion 19b may be appropriately set. For example, the protruding portion 19b may have a rectangular shape (illustrated example), a quadrangular shape other than a rectangular shape, a polygonal shape other than the rectangular shape, a circular shape, or an elliptical shape. The protruding portion 19b may be projected with a constant width (example in the figure), or the width may be changed such that the width becomes narrower toward the tip. The edge of the tip of the protrusion 19b may be a straight line orthogonal to the facing direction (D2 direction in the illustrated example) of the pair of facing electrodes 19 (illustrated example), and the width is narrower toward the tip side. The corners or curves may be formed so as to be. The protruding direction of the protruding portion 19b may be parallel to the facing direction of the pair of facing electrodes 19 (example in the figure), or may be inclined with respect to the facing direction.

The dimensions of the protrusion 19b may be set as appropriate. For example, the width of the protruding portion 19b (the length in the D1 direction in the illustrated example) may be smaller, equal to, or larger than the width of the electrode finger 15 (length in the D1 direction). good. In other words, the width of the narrowest gap G3 (the length in the direction orthogonal to the opposite direction of the pair of opposing electrodes 19; the length in the D1 direction in the illustrated example) is the width of the gap G2 (orthogonal to the electrode finger 15). It may be small, equivalent, or large with respect to the length in the direction in which it is formed.

The number of protrusions 19b and the distance s4 between the protrusions 19b may be appropriately set. In the illustrated example, two protrusions 19b are provided. Further, in the illustrated example, the interval s4 is relatively wide, for example, wider than the interval s3 and wider than the intervals s1 and s2. More specifically, for example, the interval s4 may be at least twice the interval s1. Of course, the interval s4 may be smaller than at least one of the intervals s1 to s3.

In another aspect, the total length of the width of the plurality of (two in the illustrated example) protrusions 19b and the spacing s4 of one or more (number of protrusions 19b-1) between the plurality of protrusions 19b. Is shorter than the sum of the width of the same number of electrode fingers 15 as the number of protrusions 19b and the interval s1 of one or more (number of electrode fingers 15-1) between the same number of electrode fingers 15. It may be the same, it may be equivalent, or it may be longer. In the illustrated example, the former may be longer than the latter, for example, 1.5 times or more.

In the illustrated example, the shapes and dimensions of the two counter electrodes 19 are the same as each other. However, the shape and / or the dimension may be different between the two counter electrodes 19. Further, in the illustrated example, the shapes and dimensions of the plurality of protrusions 19b of one facing electrode 19 are the same as each other. However, they may be different from each other. In the illustrated example, the plurality of gaps G3 between the tips of the plurality of protrusions 19b of one facing electrode 19 and the tips of the plurality of protrusions 19b of the other facing electrode 19 are sized and spaced s3 in the D1 direction. Are the same as each other. However, they may be different from each other.

The shape of the counter electrode 19 may be a shape other than the shape shown in the figure. For example, the shape of the counter electrode 19 may be rectangular. Then, the short sides or the long sides may face each other via the gap G3. Further, the shape of the counter electrode 19 may be a polygonal shape (including the above-mentioned rectangle). Then, the sides or the corners may face each other through the gap. Further, the counter electrode 19 may have a circular shape or an elliptical shape. Further, the shape of the pair of counter electrodes 19 may be a pair of comb teeth arranged so as to mesh with each other, similarly to the pair of comb tooth electrodes 11. In each facing electrode 19, the length of the pair of facing electrodes 19 in the facing direction and the length in the direction orthogonal to the facing direction may be the same, or one may be longer than the other.

The direction in which the pair of facing electrodes 19 face each other is arbitrary. For example, the direction in which the pair of facing electrodes 19 face each other may be the propagation direction of the elastic wave (D1 direction), the direction orthogonal to the propagation direction (illustrated example), or the propagation direction. It may be in the direction of inclining. In the illustrated example, the pair of counter electrodes 19 face each other in only one direction (D2 direction only). However, as understood from the fact that the pair of counter electrodes 19 may be a pair of comb tooth electrodes that mesh with each other, the pair of counter electrodes 19 have a portion facing each other in the D1 direction via a gap. It may have a portion facing each other in the D2 direction via a gap. That is, the pair of facing electrodes 19 may face each other in two or more directions.

The size of the arrangement region of the polarization electrode 9 (the size of the polarization electrode 9 in a plan view) may be appropriately set. For example, the arrangement region of the polarization electrode 9 may be made smaller than the arrangement region of any one of the one or more IDT electrodes 7 to which the polarization electrodes 9 are connected in parallel, or all the arrangement regions. (Example in the figure), they may be equivalent or larger. For example, the area of the arrangement region of the polarization electrode 9 is 1 with respect to the area of any one of the one or more IDT electrodes 7 to which the polarization electrodes 9 are connected in parallel, or the area of all the arrangement regions. It may be 2 or less. The arrangement region of the polarization electrode 9 (or one IDT electrode 7) may be defined by, for example, the smallest convex polygon that includes the polarization electrode 9 (or one IDT electrode 7). The area of the arrangement area of the plurality of IDT electrodes 7 may be the sum of the areas of the arrangement areas of each IDT electrode 7.

(Interval between counter electrodes)
The narrowest distance among the distances s3 between the two counter electrodes 19 is, for example, the narrowest distance between the two comb tooth electrodes 11 in each IDT electrode 7 among the distances s1 and s2 for one or more IDT electrodes 7. It is narrower than the total value. The one or more IDT electrodes 7 referred to here are all IDT electrodes 7 connected in parallel to the polarization electrode 9. Therefore, for example, three IDT electrodes 7 and a polarization electrode 9 are connected in parallel, the narrowest interval among the IDT electrodes 7 is the interval s2, and the interval s2 is mutual between the three IDT electrodes 7. When they are the same, s3 <3 × s2. As a matter of course, the narrowest portion and / or interval of each IDT electrode 7 may be the same or different between the IDT electrodes 7. The degree of difference between the narrowest interval s3 and the above-mentioned total value of the narrowest interval s1 or s2 may be appropriately set. For example, the former may be 0.9 times or less or 0.5 times or less of the latter.

The narrowest spacing of the spacing s3 between the two counter electrodes 19 is the narrowest spacing of the spacing s1 and s2 between the two comb tooth electrodes 11 and all connected in parallel with the polarization electrode 9. It may be narrow, equal, or wide with respect to the narrowest distance among the IDT electrodes 7 of the above (illustration example). When the narrowest spacing s3 is wider than the narrowest spacing s1 or s2 among the plurality of IDT electrodes 7, the degree of difference between the two may be appropriately set. For example, the former may be 1.1 times or more or 1.5 times or more of the latter. If the interval s3 is made too narrow, there is a risk of ESD destruction or defects during manufacturing. Therefore, the interval s3 may be set within a technically common sense range.

(Relationship between polarization electrode and IDT electrode)
The polarization electrode 9 is connected in parallel with the IDT electrode 7. As with the IDT electrode 7, when the polarization electrode 9 is connected, the connection is made in such a manner that a voltage is applied to the pair of counter electrodes 19 unless otherwise specified. Therefore, when the polarization electrode 9 is connected in parallel to one IDT electrode 7, for example, one comb tooth electrode 11 and one counter electrode 19 of the one IDT electrode 7 are directly or another. It is indirectly connected via an electronic element (for example, another IDT electrode 7), and the other comb tooth electrode 11 of the one IDT electrode 7 and the other counter electrode 19 are directly or indirectly via another electronic element. Refers to the connection mode connected to.

In this embodiment, more specifically, the polarization electrodes 9 are connected in parallel to all of the plurality of IDT electrodes 7 connected in series with each other. That is, one counter electrode 19 is connected to the comb tooth electrode 11 located on the one end side of the IDT electrode 7 located on the most one end side of the electrical path configured by connecting a plurality of IDT electrodes 7 in series. Has been done. The other counter electrode 19 is connected to the comb tooth electrode 11 located on the other end side of the IDT electrode 7 located on the other end side of the electrical path.

The connection between the IDT electrode 7 and the polarization electrode 9 is made directly, for example. That is, no other electronic element is interposed between the two, and only the wiring 21 is interposed. Examples of the electronic element include an IDT electrode 7, a resistor, a capacitor, and an inductor. However, for example, another electronic element may be interposed between the IDT electrode 7 and the polarization electrode 9 in such a manner that at least one of the actions described below is maintained to some extent. For example, an electronic element capable of transferring an electric charge from the comb tooth electrode 11 to the counter electrode 19 may intervene. Examples of such electronic elements include resistors and inductors.

The relative positions of the IDT electrode 7 and the polarization electrode 9 on the upper surface 3a of the piezoelectric body 3 may be appropriately set. For example, the polarization electrode 9 may be located in the D1 direction with respect to the IDT electrode 7 (in the illustrated example), may be located in the D2 direction, or may be located in the direction inclined in the D1 direction and the D2 direction. You may. Further, the polarization electrode 9 may or may not be adjacent to the IDT electrode 7. In other words, another electronic element, wiring 21, or the like may or may not be interposed between the polarization electrode 9 and the IDT electrode 7. Further, the distance between the polarization electrode 9 and the IDT electrode 7 may be long or short.

In the illustrated example, the polarization electrode 9 is located in the propagation direction (D1 direction) of the elastic wave with respect to the IDT electrode 7. Here, as described above, the IDT electrode 7 may be configured as a 1-port resonator, a vertically coupled multiple mode filter, or a transversal filter. .. As can be seen from this, in the positional relationship shown in the figure, a reflector and / or another IDT electrode 7 may be interposed between the polarization electrode 9 and the IDT electrode 7, and such Other electronic elements may not be present.

Further, in the illustrated example, the polarization electrode 9 is located in a range in which one or more IDT electrodes 7 connected in parallel to the polarization electrode 9 are located in the direction orthogonal to the propagation direction of the elastic wave (D2 direction). It fits. From another point of view, the narrowest part of the gap G3 is located within the above range. In such a case, the polarization electrode 9 or the narrowest gap G3 may be located in any of the above ranges. In the illustrated example, the narrowest gap G3 is located outside the gap G2. The outside of the gap G2 is the range of the intersection width W, the arrangement range of the dummy electrodes 17, and the arrangement range of the bus bar 13.

(wiring)
The path of the wiring 21 connecting the IDT electrode 7 and the polarization electrode 9 is appropriately determined according to the relative position between the IDT electrode 7 and the polarization electrode 9, the arrangement of other elements (for example, another IDT electrode 7 or a reflector), and the like. It may be extended by any route. Further, the wiring 21 may have a portion that crosses over with other wiring or the like via an insulating layer. The width of the wiring 21 may or may not be constant with respect to the position in the direction in which the signal flows.

The specific size of the width of the wiring 21 may be appropriately set. For example, the width of the wiring 21 may be narrower (illustrated example), equal to, or wider than the width of the counter electrode 19 (length in the D1 direction in the illustrated example). Further, the width of the wiring 21 may be narrower, equal to, or wider than the width of the connecting portion connecting the plurality of IDT electrodes 7 connected in parallel to the polarization electrode 9. In the example of FIG. 1, the width of the connection portion is the length of the bus bar 13 shared by the adjacent IDT electrodes 7 in the D1 direction. The wiring 21 is smaller than the length of the bus bar 13 in the D1 direction. The width of the wiring 21 may be, for example, 0.9 times or less, 0.5 times or less, or 0.1 times or less with respect to the width of the counter electrode 19 and / or the width of the connection portion.

When the width of the wiring 21 and / or the width of the connection portion connecting the plurality of IDT electrodes 7 is not constant with respect to the position in the direction in which the signal flows, the above description may be made, for example, between the narrowest portions. May be applied to. The width of the wiring 21 has been described in comparison with a connection portion connecting a plurality of IDT electrodes 7, but the above description describes the IDT electrode 7 and the terminal (for example, the antenna terminal 103, the transmission terminal 105 or the transmission terminal 105 shown in FIG. 10 described later). It may be used for comparison with the connection portion connected to the receiving terminal 107).

(Piezoelectric)
The piezoelectric body 3 is composed of, for example, a single crystal having piezoelectricity. Examples of the material constituting such a single crystal include lithium tantalate (LiTaO ₃ , hereinafter may be abbreviated as LT), lithium niobate (LiNbO ₃ , hereinafter may be abbreviated as LN) and the like. A crystal (SiO ₂ ) can be mentioned. The cut angle, planar shape and various dimensions may be set as appropriate. For example, the upper surface 3a of the piezoelectric body 3 may be a plane of rotation Y-cut X propagation. In this case, the X-axis is parallel to the upper surface 3a, the Y-axis is tilted at a predetermined angle with respect to the upper surface 3a, and the Z-axis is tilted at the predetermined angle with respect to the normal of the upper surface 3a. There is. The piezoelectric body 3 may be composed of polycrystals.

FIG. 2 is a cross-sectional view taken along the line II-II of FIG.

As shown in this figure, the piezoelectric body 3 may be a part of the upper surface side of the substrate 23. The configuration of the substrate 23 may be appropriate. In the illustrated example, the substrate 23 has a support substrate 25, a multilayer film 27 located on the support substrate 25, and a film-like piezoelectric body 3 (piezoelectric film) located on the multilayer film 27. .. The multilayer film 27 is configured by laminating a plurality of acoustic films 29. The acoustic films 29 adjacent to each other in the stacking direction have different impedances from each other.

Various configurations of the substrate 23 other than the illustrated example are possible. For example, the substrate 23 may have a configuration in which the upper surface of the support substrate 25 and the lower surface of the piezoelectric substrate as the piezoelectric body 3 are directly or indirectly bonded to each other via an adhesive. In this configuration, a cavity that overlaps with the IDT electrode 7 in planar fluoroscopy may or may not be configured between the piezoelectric substrate and the support substrate 25. Further, the entire substrate 23 may be composed of the piezoelectric body 3. The piezoelectric body 3 may form the entire upper surface of the substrate 23, or may form only a part of the upper surface of the substrate 23.

The thickness t0 of the piezoelectric body 3 may be appropriately set according to the electrical characteristics required for the element (for example, a resonator or a filter) configured by the IDT electrode 7. For example, the thickness t0 may be 4p or less, 2p or less, or 1p or less, and conversely, it may be more than 4p. In addition, in the embodiment in which the configuration of the substrate 23 is the configuration shown in the figure or the configuration in which the support substrate 25 and the piezoelectric substrate (piezoelectric body 3) are bonded together, the strength of the substrate 23 is ensured even if the thickness t0 is reduced. It is easy to do.

(Polarization direction of piezoelectric material)
FIG. 3A is a cross-sectional view taken along the line IIIa-IIIa of FIG. FIG. 3B is a cross-sectional view taken along the line IIIb-IIIb of FIG. In these figures, for convenience, hatching indicating that the cross section is used is omitted.

The arrows in the figure indicate the polarization direction. As can be seen from FIGS. 3 (a) and 3 (b), the polarization direction of the polarization electrode 9 immediately below the gap G3 is different from the polarization direction of the other regions. More specifically, in the illustrated example, the former polarization direction and the latter polarization direction are parallel to each other and opposite to each other.

The polarization direction may be set to an appropriate direction with respect to the upper surface 3a of the piezoelectric body 3, and the method for realizing the setting may also be appropriate. For example, in a single crystal, the direction of polarization is determined by the crystal orientation. For example, in LT or LN, the polarization direction is parallel to the Z axis. Therefore, the relationship between the upper surface 3a and the polarization direction is determined by the cut angle. In the illustrated example, the embodiment in which the piezoelectric body 3 of the rotary Y-cut X propagation is used is exemplified, and the polarization direction (Z axis) is around the D1 axis with respect to the normal line (D3 direction) of the upper surface 3a. It is tilted in the direction of rotation. The direction of the polarization direction parallel to the Z axis (+ Z side or −Z side) may be realized, for example, by applying a voltage to the piezoelectric body 3. Further, when the piezoelectric body 3 is a polycrystal, the polarization direction may be set in an arbitrary direction by applying a voltage.

Immediately below the gap G3, the polarization direction does not have to be completely different from the polarization direction of the other region. For example, in the immediate vicinity of the gap G3 and / or in other regions, a plurality of minute portions having different polarization directions may be mixed. Then, when viewed on average or when focusing on most of the gap G3, the polarization directions may be different between the region directly below the gap G3 and the other regions. In other words, in each region, the direction with the strongest polarization may be specified as the polarization direction. When the piezoelectric body 3 is a polycrystal, the above-mentioned minute portions may be crystal grains.

Immediately below the gap G3, the depth at which the polarization direction is different from the polarization directions of the other regions may be appropriately set. For example, the depth may be the entire thickness of the piezoelectric body 3 (illustrated example), or may be a part of the upper surface 3a side of the piezoelectric body 3. Further, as can be understood from the above-mentioned explanation that minute portions having different polarization directions may be mixed, the strength of polarization in a direction different from the polarization direction of other regions immediately below the gap G3 is the depth. It may or may not be constant in the direction.

Immediately below the gap G3, the region whose polarization direction is different from the polarization direction of the other region may extend over the entire gap G3 between the pair of counter electrodes 19, or may extend only a part thereof. .. As an example of the latter, in the shape of the polarization electrode 9 shown in FIG. 1, the tip of the protruding portion 19b of one facing electrode 19 and the protruding portion of the other facing electrode 19 in the gap G3 of the entire pair of facing electrodes 19 An embodiment in which the polarization direction is different from the polarization direction of other regions is given only in the portion between the tip of 19b (referred to as the first portion in this paragraph) or only in the first portion and its surroundings. be able to. When each protrusion 19b is two or more, there are two or more first portions. In this case, the polarization direction differs from the polarization direction of the other regions only in the portion between the two or more first portions and the two or more first portions, or only in these portions and their surroundings. May be. As can be understood from the above-mentioned explanation that minute portions having different polarization directions may be mixed, in a region where the polarization direction is different from the polarization direction of other regions, the polarization in a direction different from the polarization direction of other regions. The strength of is may or may not be constant with respect to the position in the plan view.

The polarization direction may be the same over the entire first region in all regions of the upper surface 3a of the piezoelectric body 3 except the region directly below the gap G3 (referred to as the first region in this paragraph). However, they do not have to be the same. From another point of view, the "other region" whose polarization direction is compared with the region directly below the gap G3 may be the entire upper surface 3a or a part of the upper surface 3a. As a part of the upper surface 3a, for example, at least one or all the arrangement regions of one or more IDT electrodes 7 to which the polarization electrodes 9 are connected in parallel may be used.

Further, even in other regions that are a part of the upper surface 3a as described above, the polarization directions may or may not be the same over the entire other regions. In other words, the other regions may be regions that have the same polarization direction when viewed on average or for most of the other regions. For example, in an area of 20% or less, 10% or less, 5% or less or 1% or less of the area of the other region, even if the polarization direction is different from the region of the remaining area (that is, most of the other region). good. The polarization direction different from the polarization direction of most of the other regions may be the same as or different from the polarization direction directly below the gap G3. A region having a polarization direction different from most of the other regions is, for example, in at least one or all of the arrangement regions of one or more IDT electrodes 7 in which the other region is connected in parallel with the polarization electrode 9. In some cases, it may be part of a plurality of gaps G2.

As can be understood from the above description, when the polarization direction in the region immediately below the gap G3 is different from the polarization direction in another region (for example, the region where the IDT electrode 7 is arranged), for example, the former Only a part of the region in the plan view and a part of the latter region in the plan view may differ in the polarization direction, or a part of the piezoelectric body 3 in the thickness direction (however, the upper surface 3a may be used. Including), the polarization directions may only be different.

(Production method)
The manufacturing method of the elastic wave device 1 may be an application of a known manufacturing method or a known manufacturing method, except that, for example, a polarization electrode 9 is provided. Even with a known manufacturing method, the polarization direction directly under the gap G3 can be made different from the polarization direction of other regions by the action of the polarization electrode 9. For example:

FIG. 4 is a flowchart showing an outline of the procedure of the manufacturing method of the device 1.

In step ST1, wafers (not shown) to be a plurality of piezoelectric bodies 3 (a substrate 23 from another viewpoint) are prepared. At this point, the polarization directions are aligned over the entire surface of the wafer (in another aspect, over the entire surface of each piezoelectric 3). The polarization directions may be aligned, for example, in the process of growing the crystal and / or by applying a voltage after the crystal has grown.

In step ST2, a conductor layer 5 (in other words, an IDT electrode 7 and a polarization electrode 9) is formed on a region of the wafer to be a plurality of piezoelectric bodies 3. For example, the conductor layer may be formed on the entire surface of the wafer by a physical vapor deposition method or a chemical vapor deposition method, and then the conductor layer may be etched via a mask (resist) formed by photolithography. Alternatively, the conductor layer may be formed by a physical vapor deposition method or a chemical vapor deposition method via a mask (resist) formed by using photolithography.

In step ST3, a voltage is applied to the polarization electrode 9 to make the polarization direction directly below the gap G3 different from the original direction. This step ST3 may be, for example, a known step performed after electrode formation. In other words, step ST3 does not have to be a step performed for the purpose of polarization. However, step ST3 is a step that involves a temperature change. For example, step ST3 may be a step of removing the above-mentioned mask and drying the wafer.

In the above steps, when the temperature of the wafer changes, the piezoelectric body 3 is charged due to the pyroelectric effect of the piezoelectric body 3. This charge flows through the conductor layer 5, and thus a voltage is applied to the two counter electrodes 19. As a result, the polarization direction changes immediately below the gap G3. For example, in the example shown in FIG. 3B, the direction of the polarization direction is reversed by applying an electric field from the −D2 side to the + D2 side to the piezoelectric body 3.

Note that step ST3 may be a step aimed at applying a voltage to the polarization electrode 9. Further, in order to easily change the polarization direction in the gap G3, some damage may be given to the region of the upper surface 3a of the piezoelectric body 3 directly below the gap G3 before applying the voltage to the polarization electrode 9. .. For example, plasma, chemicals or laser light may damage the area.

In step ST4, the wafer is fragmented into a plurality of piezoelectric bodies 3. Individualization may be realized by, for example, a known method such as dicing, or a method applying a known method. It is not always necessary to follow the step of FIG. 4, and ST3 may be performed after ST4, for example. However, it may be after the elastic wave device is completed.

Although not particularly shown, the method for manufacturing the device 1 includes various steps such as a step of forming a protective film covering the conductor layer 5 and / or a step of forming a package in addition to the above steps. good.

As described above, the device 1 according to the present embodiment includes the piezoelectric body 3, the IDT electrode 7 located on the upper surface 3a of the piezoelectric body 3, and the IDT electrode 7 located on the upper surface 3a of the piezoelectric body 3. It has a polarization electrode 9 connected in parallel. The polarization electrode 9 has two counter electrodes 19 facing each other via a gap G3. In the piezoelectric body 3, the polarization direction in the region immediately below the gap G3 is different from the polarization direction in the region in which the IDT electrode 7 is arranged.

Therefore, for example, the characteristics of the device 1 can be improved. Specifically, it is as follows.

First, we focus on the manufacturing method. As mentioned in the description of step ST3, after the electrode is formed, the piezoelectric body 3 may generate an unintended charge due to the temperature change. For this charge, for example, a voltage is applied to the IDT electrode 7, and an electric field is applied to a region of the upper surface 3a of the piezoelectric body 3 directly below the gaps G1 and G2. As a result, the polarization direction changes in the region directly below the gaps G1 and / or G2. Such a change in the polarization direction affects the characteristics of the element (for example, a resonator or a filter) configured by the IDT electrode 7. For example, in the experiment of the inventor of the present application, ripple occurred in the passing characteristics of the filter using the IDT electrode 7.

However, when the polarization electrode 9 is provided, the charge of the IDT electrode 7 is released to the polarization electrode 9, and a current is substantially passed along with the change in the polarization of the gap G3 (for example, the polarization inversion) to neutralize the charge. be able to. As a result, in the gaps G1 and / or G2, the area of the region where the polarization direction changes is reduced, and / or the strength of the polarization in the changed polarization direction is reduced. As a result, the probability that the characteristics of the IDT electrode 7 will deteriorate due to the change in the polarization direction is reduced. From the above, when the completed device 1 is viewed, the fact that the polarization direction is different from the polarization direction of the arrangement region of the IDT electrode 7 directly under the gap G3 means that the polarization direction in the arrangement region of the IDT electrode 7 It can be said that the characteristics of the device 1 are improved by reducing the change in the device 1 to some extent.

Next, pay attention to the device 1 after completion. Elastic waves generated in the arrangement region of the IDT electrode 7 may leak to the outside of the arrangement region of the IDT electrode 7. This leaked elastic wave reflects, for example, returns to the arrangement region of the IDT electrode 7 or reaches the arrangement region of another IDT electrode 7, thereby causing ripples in the characteristics of the element configured by the IDT electrode 7. It becomes a factor. However, if the polarization directions are different in the region directly below the gap G3 in the upper surface 3a of the piezoelectric body 3, the phase and / or direction of the elastic wave leaking to the region directly below the gap G3 is likely to be disturbed. As a result, for example, the influence of the elastic wave leaking to the region immediately below the gap G3 and the elastic wave leaking to another region on the characteristics of the device 1 is less likely to be added, and the magnitude of the ripple can be reduced.

Further, in the portion where the polarization direction has changed, the change is more likely to proceed or return due to the application of the voltage. As a result, it reacts swiftly to the pyroelectric voltage generated after commercialization, and the polarization direction changes at the IDT electrode 7. The present embodiment can reduce such probability, for example.

Further, for example, even-order nonlinear strains (for example, second-order harmonics and second-order complementary modulation strains) that occur in a portion where the polarization direction changes have the opposite phase to those generated in the IDT electrode 7, and thus are comprehensive. Non-linear distortion is reduced, resulting in an elastic wave device with less noise.

In device 1, the IDT electrode 7 has a plurality of electrode fingers 15 arranged at a predetermined pitch p (as described above, most of the pitch p or the average value of the pitch p may be referred to). You can do it. The thickness t0 of the piezoelectric body 3 may be twice or less the pitch p.

In this case, for example, it is easy to make the polarization direction in the region immediately below the gap G3 different from the polarization direction in the arrangement region of the IDT electrode 7. Specifically, when the piezoelectric body 3 is relatively thick, even if a voltage is applied to the upper surface 3a to make the polarization direction different only in the vicinity of the upper surface 3a, then the polarization direction in the vicinity of the upper surface 3a is the polarization of the lower portion. It is easily affected by the direction and returns to its original state. Therefore, in order to maintain the state in which the polarization direction is changed, the voltage applied to the polarization electrode 9 in step ST3 is increased and / or an electrode different from the polarization electrode 9 (for example, the piezoelectric body 3 is placed in the thickness direction). It becomes necessary to apply an electric field to the piezoelectric body 3 by the pair of electrodes sandwiched between them). However, when the piezoelectric material 3 is relatively thin, such a need is reduced.

As can be understood from the above, in the elastic wave device having a relatively thick piezoelectric body, even if an electrode similar to the polarization electrode 9 is provided, the polarization direction of the region directly under the electrode is intentionally set. The polarization direction is constant over the entire upper surface of the piezoelectric body unless some treatment is performed to make it different from the polarization direction in other regions. That is, a known elastic wave device having an electrode similar to the polarization electrode 9 does not have the same configuration as the device 1.

Further, the phenomenon (problem) that the polarization direction changes between the pair of comb-tooth electrodes 11 due to the electric charge generated by the temperature change in the manufacturing process and the characteristics of the element composed of the IDT electrode 7 deteriorates is compared. It does not occur in known elastic wave devices having thick piezoelectric materials. The fact that the above phenomenon (problem) occurs when the piezoelectric material is thin is a finding discovered by the inventor of the present application who is searching for the cause of the deterioration of the characteristics, and is not a finding generally known in the field of elastic wave devices. ..

The device 1 may have a plurality of IDT electrodes 7 connected in series with each other. The polarization electrode 9 may be connected in parallel to the entire plurality of IDT electrodes 7. Each of the plurality of IDT electrodes 7 may have two comb tooth electrodes 11 that are in mesh with each other. The narrowest spacing s3 between the two counter electrodes 19 may be narrower than the sum of the narrowest spacing s1 or s2 between the two comb tooth electrodes 11 for the plurality of IDT electrodes 7.

In this case, for example, it is easy to change the polarization direction directly under the gap G3 of the polarization electrode 9 by the electric charge generated due to the temperature change. From another aspect, it is facilitated to reduce the probability that a change in the polarization direction will occur immediately below the gaps G1 and / or G2 of the IDT electrode 7. Specifically, it is as follows.

FIG. 5 is a plan view illustrating a change in the polarization direction in the device 1A according to the comparative example.

The device 1A differs from the device 1 according to the embodiment only in that it does not have the polarization electrode 9. The device 1A is manufactured by the same manufacturing method as that of the manufacturing method according to the embodiment described with reference to FIG. 3, except that the polarization electrode 9 is not provided, for example. At this time, as described above, the polarization direction in the gaps G1 and / or G2 may change due to the electric charge caused by the temperature change. In FIG. 5, the distribution in the polarization direction obtained by the analysis of the prototype device 1A is schematically shown.

In FIG. 5, the plurality of regions R1 shown by hatching are regions in which the polarization direction has changed. Specifically, the piezoelectric body 3 of the prototype device 1A is made of a single crystal of LT, and the polarization direction is parallel to the Z-axis direction. The polarization direction of the region R1 is opposite to the polarization direction of the other regions.

In the prototype device 1A, the change in the polarization direction (polarization inversion) occurred in a plurality of regions R1 including the region directly below the gap G2 between the tip of the electrode finger 15 and the tip of the dummy electrode 17. The size of the plurality of regions R1 is not constant. Further, in the plurality of IDT electrodes 7, the number of regions R1 is different from each other.

As a result of consideration about the size and distribution of the region R1 as described above, the inventor of the present application has found the following matters. The total area of the region R1 in each IDT electrode 7 is equivalent among the plurality of IDT electrodes 7. From this, as shown by the arrow y1, the current flows through the plurality of IDT electrodes 7 connected in series, and the current (total charge amount) flowing between the plurality of IDT electrodes 7 is the same. From another point of view, it can be considered that a charge is generated at both ends of the entire plurality of IDT electrodes 7 connected in series.

Therefore, for example, even if the polarization electrode 9 is connected in parallel to the entire plurality of IDT electrodes 7 connected in series, it is possible to reduce the probability that a change in the polarization direction will occur in each IDT electrode 7. .. As a result, the pattern of the conductor layer 5 can be simplified as compared with, for example, an embodiment in which the polarization electrode 9 is provided in each IDT electrode 7 (the embodiment may also be included in the technique according to the present disclosure). ..

Further, for example, the voltage applied to the entire plurality of IDT electrodes 7 connected in series is divided. Therefore, even if the narrowest spacing s3 of the polarization electrodes 9 is not narrower than the narrowest spacing s2 (or s1) of the individual IDT electrodes 7, it is greater than the total value for the plurality of IDT electrodes 7 of the narrowest spacing s2. If it is narrowed, there is a high probability that a change in the polarization direction will occur immediately below the gap G3. From another viewpoint, the charge of the IDT electrode 7 can be neutralized in the polarization electrode 9 to reduce the probability that the change in the polarization direction occurs in the IDT electrode 7.

The narrowest distance s3 between the two counter electrodes 19 is the narrowest distance between the two comb tooth electrodes 11 meshing with each other, s1 or s2, and is the narrowest among the plurality of IDT electrodes 7. The interval may be wider than s1 or s2.

Even in this case, as described above, if the narrowest interval s3 is narrower than the total value of the narrowest interval s1 or s2, the polarization electrode 9 can cause a change in the polarization direction to neutralize the charge. On the other hand, since the narrowest spacing s3 is wider than the narrowest spacing s1 or s2 among the plurality of IDT electrodes 7, the capacitance of the polarization electrode 9 can be reduced. As a result, the influence of the capacitance of the polarization electrode 9 on the characteristics of the element configured by the IDT electrode 7 is reduced.

The two counter electrodes 19 may face each other in only one direction (D2 direction in the example of FIG. 1).

In the piezoelectric body 3, the voltage application direction in which the polarization direction is likely to change and the voltage application direction in which the polarization direction is unlikely to change due to the relationship between the original polarization direction (polarization direction in step ST1) and the upper surface 3a, etc. And may exist. Therefore, when the configuration of the polarization electrode 9 is such that the two counter electrodes 19 face each other in only one direction, a voltage application direction in which the polarization direction is likely to change can be selected as the one direction. As a result, for example, in step ST3, the polarization direction directly under the gap G3 is changed to facilitate the flow of an electric current. From another viewpoint, the two facing electrodes are compared with a configuration in which the polarization electrodes 9 face each other in two or more directions like a comb tooth electrode (the embodiment may also be included in the technique according to the present disclosure). The amount of charge that can be neutralized can be made relatively large with respect to the capacity of 19.

The device 1 may have a first connection portion and a second connection portion. The first connection portion is a portion connecting an IDT electrode 7 connected in parallel to the polarization electrode 9 and another IDT electrode 7 or a terminal. In the example of FIG. 1, adjacent IDT electrodes 7 are connected to each other. It is a bus bar 13 shared by. The second connection portion is a portion connecting the IDT electrode 7 and the polarization electrode 9, and is the wiring 21 in the example of FIG. 1. The width of the second connection portion (wiring 21) may be narrower than the width of the first connection portion (the length of the bus bar 13 in the D1 direction in the example of FIG. 1).

In this case, for example, the resistance value of the wiring 21 becomes relatively large. As a result, when a signal is input to the IDT electrode 7, the signal is less likely to flow to the polarization electrode 9. As a result, the probability that the polarization electrode 9 has an unintended effect on the characteristics of the element (for example, a resonator or a filter) configured by the IDT electrode 7 is reduced.

Each of the two comb tooth electrodes 11 is located between the bus bar 13, the plurality of electrode fingers 15 extending in parallel with each other in the first direction (D2 direction), and the plurality of electrode fingers 15 from the bus bar 13. It may have a dummy electrode 17 protruding in the D2 direction. The bus bars 13 of the two comb tooth electrodes 11 may face each other. The plurality of electrode fingers 15 of the two comb tooth electrodes 11 may be arranged alternately. The tips of the plurality of electrode fingers 15 of one comb tooth electrode 11 and the tips of the dummy electrodes 17 of the other comb tooth electrode 11 may face each other via a tip gap (gap G2). The narrowest portion of the gap G3 of the polarization electrode 9 may be within the range in which one or more IDT electrodes 7 to which the polarization electrodes 9 are connected in parallel are located in the D2 direction, and the one or more. It may be located outside the range in which the gap G2 of the IDT electrode 7 is located.

In the gap G2, turbulence of elastic waves is relatively likely to occur in the arrangement region of the IDT electrode 7. On the other hand, as described above, since the polarization direction of the region immediately below the gap G3 is different from that of the other regions, the leaked elastic wave can be disturbed and the ripple can be reduced. Therefore, when the position of the gap G3 deviates from the position of the gap G2, the effect of disturbing the leaked elastic wave is improved.

In the present embodiment, from another aspect, the method for manufacturing the device 1 includes an electrode forming step (ST2) and a subsequent polarization step (ST3). In the electrode forming step, the IDT electrode 7 and the polarization electrode 9 connected in parallel to the IDT electrode 7 are formed on the piezoelectric body 3 whose polarization directions are aligned over the entire surface. In the polarization step, a temperature change is caused in the piezoelectric body 3, a voltage is applied to the two counter electrodes 19 by the electric charge generated by the pyroelectric effect, and the IDT electrode 7 is arranged in the polarization direction in the region directly below the gap G3. It is different from the polarization direction in the region.

Therefore, the above-mentioned device 1 can be easily realized. From another viewpoint, it is possible to reduce the probability that the polarization direction changes immediately below the gap G1 or G2 of the IDT electrode 7 due to the temperature change.

<Second Embodiment>
FIG. 6 is a plan view schematically showing the configuration of the main part of the device 201 according to the second embodiment.

The device 201 has the reflector 31, which was also mentioned in the first embodiment. The device 201 is different from the device 1 of the first embodiment in that the polarization electrode is realized by the reflector 31. Specifically, for example, it is as follows.

(Reflector)
The device 201 has, for example, a reflector 31 located in the propagation direction (D1 direction) of elastic waves with respect to each IDT electrode 7. In the illustrated example, three reflectors 31 are shown on one side (−D1 side) in the D1 direction with respect to the three IDT electrodes 7. The reflector 31 may be provided on both sides in the D1 direction with respect to the IDT electrode 7, as will be understood from the configuration of the 1-port resonator 37 (FIG. 10) described later. Further, as can be understood from the vertically coupled multiple mode type filter 39 (FIG. 10) and the transversal type filter (not shown), it may be provided only on one side in the D1 direction with respect to the IDT electrode 7.

The material and thickness of the reflector 31 are, for example, the same as the material and thickness of the IDT electrode 7. The reflector 31 is formed in a grid pattern, for example. That is, the reflector 31 includes a pair of bus bars 33 facing each other and a plurality of strip electrodes 35 extending between the pair of bus bars 33. Since FIG. 6 is a schematic diagram, the number of strip electrodes 35 is shown to be small, as in the case of the electrode fingers 15. In practice, more strip electrodes 35 may be arranged than shown.

The configuration of the bus bar 33 may be basically the same as that of the bus bar 13 of the IDT electrode 7, for example. Therefore, the description of the bus bar 13 may be appropriately referred to the bus bar 33 as long as there is no contradiction or the like. Of course, since the specific action required for the IDT electrode 7 and the reflector 31 is different, there may be a difference between the two. For example, the length of the bus bar 33 in the D1 direction is set according to the characteristics required for the reflector 31, and is usually different from the length of the bus bar 13. Further, the position and / or width (length in the D2 direction) of the bus bar 33 in the D2 direction may be slightly different from that of the bus bar 13.

The configuration of the strip electrode 35 may be substantially the same as the configuration of the electrode finger 15 of the IDT electrode 7, except that the strip electrode 35 is laid between the pair of bus bars 33, for example. Therefore, the description of the electrode finger 15 may be appropriately applied to the strip electrode 35 as long as there is no contradiction or the like. Of course, since the specific action required for the IDT electrode 7 and the reflector 31 is different, there may be a difference between the two. For example, the number of strip electrodes 35 is set according to the characteristics required for the reflector 31, and is usually different from the number of electrode fingers 15. The pitch of the electrode fingers 15 and the strip electrodes 35 adjacent to each other is basically the same as the pitch p of the plurality of electrode fingers 15 and the pitch of the plurality of strip electrodes 35.

(Polarization electrode)
In the reflector 31 on the most + D2 side, all the strip electrodes 35 are divided in the middle of the length direction (D2 direction). As a result, the reflector 31 constitutes a polarization electrode 9 having a shape similar to the shape of the polarization electrode 9 illustrated in FIG. 1. Specifically, the portion on the + D2 side and the portion on the −D2 side with respect to the divided position constitute two counter electrodes 19. The bus bar 33 constitutes the base 19a. The divided one-sided portion and the other-sided portion of the strip electrode 35 each form a protruding portion 19b. At the divided position of the strip electrode 35, the narrowest portion of the gap G3 between the two counter electrodes 19 is formed.

When a plurality of reflectors 31 are provided as in the illustrated example, the reflector 31 as the polarization electrode 9 may be any reflector 31. For example, unlike the illustrated example, the central reflector 31 or the most −D2 side reflector 31 may be the polarization electrode 9.

The position and size of the gap G3 in the D2 direction at the divided position of the strip electrode 35 may be appropriately set. In the illustrated example, the range of the gap G3 in the D2 direction at the dividing position and the range of the gap G2 in the D2 direction partially overlap each other. By doing so, for example, it is possible to reduce the decrease in the reflective action of the reflector 31 due to the division of the strip electrode 35. The gap G2 in which the gap G3 and the range in the D2 direction overlap at the dividing position may be located on either the + D2 side or the −D2 side with respect to the crossing width W (see FIG. 1). Note that, unlike the illustrated example, the gap G3 at the dividing position does not have to overlap with the gap G2 in the range in the D2 direction.

The description of the interval s3 described in the first embodiment may be incorporated in the present embodiment. For example, the interval s3 (the narrowest interval s3) at the division position may be larger, equal, or smaller than the size of the interval s2 (illustrated example). When the interval s3 and the interval s2 at the divided position are equivalent, the gap G3 and the gap G2 at the divided position may all overlap each other with respect to the range in the second direction (example in the figure), or all of them may overlap each other. Do not have to overlap. When one of the interval s3 and the interval s2 at the dividing position is larger than the other, the gap G3 and the gap G2 at the dividing position may include all of the larger and smaller ones with respect to the range in the second direction. It does not have to be included.

In the illustrated example, the gap G3 at the plurality of division positions has the same position in the D2 direction and the interval s3. However, they may be different from each other. For example, by making the dividing positions of the strip electrodes 35 adjacent to each other different (for example, alternately allocating the positions of the gap G2 on the −D2 side and the positions of the gap G2 on the + D2 side), the reflecting action of the reflector 31 is reduced. Can reduce the probability that is biased to one side in the D2 direction. As shown in the illustrated example, when the positions of the gaps G3 at the divided positions are the same, the polarization direction is set to another region (for example, the arrangement region of the IDT electrode 7) even in the portion between the adjacent divided positions. ) Is easy to make different with respect to the polarization direction.

In the embodiment in which the polarization electrode 9 is realized by the reflector 31, the dividing position does not have to be the position where the strip electrode 35 is divided into two, unlike the illustrated example. For example, the connection position between the bus bar 33 and the strip electrode 35 may be set as the dividing position. In other words, the bus bar 33 and the tip of the strip electrode 35 may face each other via the gap G3.

(Connection of polarization electrodes)
The polarization electrode 9 is connected in parallel to one or more IDT electrodes 7 as in the first embodiment. Regarding this connection, in the second embodiment, the reflector 31 is used instead of the wiring 21. Specifically, it is as follows.

A plurality of reflectors 31 arranged in the D2 direction are connected in series with each other. More specifically, the bus bar 33 is shared between the adjacent reflectors 31. Further, the bus bar 33 located on the one side (-D2 side) of the reflector 31 located on one side (-D2 side) in the D2 direction extends in the D1 direction and is connected to the bus bar 13 of the IDT electrode 7. (Continuous with the bus bar 13.). Similarly, the bus bar 33 located on the other side (+ D2 side) of the reflector 31 located on the other side (+ D2 side) in the D2 direction extends in the D1 direction and is connected to the bus bar 13. On the other hand, the other bus bar 33 is separated (not connected) from the adjacent bus bar 13 in the D1 direction via the gap G5. With such a configuration, the polarization electrode 9 is connected in parallel to the entire plurality of IDT electrodes 7.

The gap (length in the D1 direction) of the gap G5 may be, for example, substantially the same as the gap s1. Further, the narrowest interval s3 may be smaller, equal to, or larger than the interval of the gap G5.

Unlike the illustrated example, the connection between the reflectors 31 may be realized by wiring connecting the bus bars 33 which are not shared. Further, the connection between the bus bar 33 and the bus bar 13 is not realized by making the bus bar 33 and the bus bar 13 continuous, but may be realized by providing wiring between them. In these cases, the wiring may be relatively thin, as in the wiring 21 of the first embodiment. The description of the wiring 21 may be incorporated into the above wiring.

Unlike the illustrated example, the connection between the IDT electrode 7 and the polarization electrode 9 may be realized without using the reflector 31. For example, the plurality of reflectors 31 may not be connected in series with each other, and the IDT electrode 7 and the polarization electrode 9 may be connected by wiring 21. In this case, two or more of the plurality of reflectors 31 may be the polarization electrodes 9.

Unlike the illustrated example, the reflector 31 that functions as wiring may be combined with a polarization electrode 9 (first embodiment) that does not also serve as the reflector 31. For example, even if the polarization electrode 9 of the first embodiment is located on the opposite side of the IDT electrode 7 with respect to the reflector 31, the IDT electrode 7 and the polarization electrode 9 are connected via the reflector 31. good.

As described above, in the present embodiment, the device 201 has the polarization electrode 9 connected in parallel with the IDT electrode 7 as in the device 1 of the first embodiment. Therefore, the same effect as that of the first embodiment is achieved. For example, the characteristics of the device 201 can be improved.

The device 201 may have a plurality of IDT electrodes 7 and a plurality of reflectors 31 adjacent to each other in the propagation direction (D1 direction) of elastic waves. The plurality of reflectors 31 may be connected in series with each other. The entire plurality of reflectors 31 may be connected in parallel to the entire plurality of IDT electrodes 7. Each of the plurality of reflectors 31 may have a plurality of strip electrodes 35 extending in parallel with each other in a direction orthogonal to the D1 direction (D2 direction). One of the plurality of reflectors 31 may be a polarization electrode 9 by being divided in the D2 direction by the plurality of strip electrodes 35.

In this case, for example, the shape of the polarization electrode 9 is the same as the shape of the polarization electrode 9 of the first embodiment. As a result, for example, the interval s3 of the polarization electrodes 9 can be reduced while reducing the capacity of the polarization electrodes 9. On the other hand, the need to newly secure a region for arranging the polarization electrode 9 on the upper surface 3a of the piezoelectric body 3 is reduced. As a result, the device 201 can be miniaturized. Further, since the number of the strip electrodes 35 is a plurality, the number of the gap G3 having the narrowest interval is also a plurality. As a result, the effect of changing the polarization direction directly under the gap G3 is improved.

<Third Embodiment>
FIG. 7 is a plan view schematically showing the configuration of the main part of the device 301 according to the third embodiment.

The device 301 is different from the device 1 of the first embodiment in that the number of IDT electrodes 7 to which the polarization electrodes 9 are connected in parallel is one. In other respects, the device 301 may be basically the same as the device 1.

The narrowest spacing s3 of the polarization electrodes 9 is the narrowest spacing s1 or s2 of each IDT electrode 7 for all of one or more IDT electrodes 7 to which the polarization electrodes 9 are connected in parallel, as in the first embodiment. It may be narrower than the total value. However, in the present embodiment, since the number of IDT electrodes 7 connected in parallel to the polarization electrode 9 is one, the narrowest spacing s3 is narrower than the narrowest spacing s1 or s2 of one IDT electrode 7. Will be done.

In the illustrated example, the shape of the polarization electrode 9 is the same as the shape of the polarization electrode 9 of the first embodiment. Further, as in the first embodiment, the IDT electrode 7 and the polarization electrode 9 are connected by the wiring 21. However, the polarization electrode 9 may be configured by the reflector 31 and / or may be connected to the IDT electrode 7 by the reflector 31 as in the second embodiment. For example, one reflector 31 may be arranged on at least one side in the D1 direction with respect to one IDT electrode. Then, the pair of bus bars 33 of one reflector 31 may be continuous with the pair of bus bars 13 of one IDT electrode 7.

As described above, in the present embodiment, the device 301 has the polarization electrode 9 connected in parallel with the IDT electrode 7 as in the device 1 of the first embodiment. Therefore, the same effect as that of the first embodiment is achieved. For example, the characteristics of the device 301 can be improved.

In this embodiment, the number of IDT electrodes 7 connected in parallel with the polarization electrode 9 is one. The IDT electrode 7 has two comb tooth electrodes 11 that mesh with each other. The narrowest spacing s3 between the two counter electrodes 19 may be narrower than the narrowest spacing s1 or s2 between the two comb tooth electrodes 11.

In this case, the polarization electrode 9 is connected only to the IDT electrode 7 of one or more IDT electrodes 7 possessed by the device 301. Here, the probability that the change in the polarization direction occurs is affected by, for example, the connection state of the IDT electrode 7 to the terminal and / or other element (in another viewpoint, the ease of charge escape). Therefore, for example, by connecting the polarization electrode 9 to one IDT electrode 7 having a high probability of a change in the polarization direction among the plurality of IDT electrodes 7, the change in the polarization direction is effectively reduced as a whole. There is expected.

<Modification example>
Hereinafter, a modified example will be described. The following modifications may be applied to any of the embodiments described so far.

(Capacity of polarization electrode)
The capacitance of the polarization electrode 9 may be appropriately set for the purpose of adjusting the characteristics of the element (for example, a resonator or a filter) composed of the IDT electrode 7, and the influence on the characteristics of the element composed of the IDT electrode 7 may be affected. It may be set to be small. For example:

FIG. 8A is a diagram schematically showing the characteristics of the resonator including the IDT electrode 7. In this figure, the horizontal axis indicates the frequency f. The vertical axis shows the absolute value of impedance | Z |. The resonator is, for example, a one-port resonator 37 (FIG. 10) having reflectors 31 on both sides of an elastic wave propagation direction (D1 direction) with respect to one IDT electrode 7.

| Z | of the resonator 37 has, for example, a minimum value at the resonance frequency fr and a maximum value at the antiresonance frequency fa. The frequency difference Δf between the resonance frequency fr and the antiresonance frequency fa is one of the items indicating the characteristics of the resonator 37. For example, in a filter (described later) in which a plurality of resonators 37 are connected in a ladder type, the total width of the pass band and the transition bands on both sides thereof is approximately twice Δf.

When a capacitor is connected in parallel to the IDT electrode 7, Δf becomes small. The polarization electrode 9 can be used as this capacitor. In this case, the capacitance of the polarization electrode 9 may be appropriately set so as to obtain a desired Δf. On the other hand, unlike the above, when the polarization electrode 9 does not affect Δf, the capacitance of the polarization electrode 9 may be relatively small.

FIG. 8B is a diagram showing an example of the influence of the capacitance of the polarization electrode 9 on the frequency difference Δf. In this figure, the horizontal axis indicates the capacitance ratio C2 / C0. The capacitance C0 is the capacitance of the IDT electrode 7. The capacitance C2 is the capacitance of the polarization electrode 9. The vertical axis shows the ratio Δf / Δf0 of the frequency Δf to the frequency Δf0. Δf0 is Δf when the capacitance C2 is 0 (in other words, when the polarization electrode 9 is not provided). The line L1 in the figure shows the change of Δf / Δf0 with respect to the change of C2 / C0.

As in this example, as the capacitance C2 increases, the frequency difference Δf decreases. From the viewpoint of reducing the influence of the polarization electrode 9 on Δf, for example, the capacitance C2 may be set so that Δf / Δf0 is 90% or more. At this time, the volume ratio C2 / C0 is 12% or less in the illustrated example.

Depending on the specific shape and dimensions of the IDT electrode 7, the specific value of the capacitance ratio C2 / C0 at which the frequency difference Δf is 90% or more is different from the example shown in FIG. 8 (b). However, the frequency difference Δf is theoretically determined by the capacitance C0 of the IDT electrode 7 and the capacitance of the series resonant circuit in the equivalent circuit of the IDT electrode 7, and is not affected by other values. Further, the capacitance C2 of the polarization electrode 9 contributes to substantially increasing C0. Then, FIG. 8B shows various values as ratios. Further, in the example of FIG. 8B, no special shape and dimensions of the IDT electrode 7 are assumed. Therefore, it can be considered that FIG. 8B holds even for a general resonator.

(Shape of polarization electrode)
FIG. 9 is a diagram showing a modified example of the shape of the polarization electrode 9.

In the description of the first embodiment, it has been stated that the number of one or more protrusions 19b of each counter electrode 19 may be arbitrary. In FIG. 9, the counter electrode 19 having a larger number of protrusions 19b than the number (2) illustrated in FIG. 1 is exemplified. In such a case, the number of protruding portions 19b may be, for example, 3 or more, 5 or more, or 10 or more.

When the number of the protruding portions 19b is increased in this way, for example, the region where the polarization direction changes becomes wider in the direction orthogonal to the direction in which the protruding portions 19b are projected (the vertical direction of the paper surface). On the other hand, since the portion facing the region where the polarization direction changes at the narrowest interval s3 is limited to the tip of the protrusion 19b, the increase in the capacitance of the polarization electrode 9 is suppressed.

Further, in the description of the first embodiment, it is described that the size of the interval s4 between the protrusions 19b is arbitrary. In FIG. 9, an interval s4 narrower than the interval s4 exemplified in FIG. 1 is exemplified. Specifically, in the example of FIG. 1, the interval s4 is wider than the interval s1 to s3, but in the example of FIG. 9, the interval s4 is set to the interval s3 or less. In this way, it becomes easy to change the polarization direction in the region in the vertical direction of the paper surface with respect to the narrowest gap G3.

<Usage example>
Hereinafter, a demultiplexer and a communication device as usage examples of the elastic wave device will be described. In the following demultiplexers and communication devices, the devices of any of the embodiments described so far may be used. However, for convenience, in the following description, device 1 may be taken as an example on behalf of devices 1, 201 and 301.

(Demultiplexer)
FIG. 10 is a circuit diagram schematically showing the configuration of the demultiplexer 101. As can be seen from the reference numerals shown in the upper left corner of the paper in FIG. 10, in this figure, the comb tooth electrode 11 is schematically shown by a bifurcated fork shape. The reflector 31 is represented by a single line with both ends bent.

The illustrated demultiplexer 101 is more specifically configured as a duplexer. The demultiplexer 101, for example, has a transmission filter 109 that filters the transmission signal from the transmission terminal 105 and outputs the signal to the antenna terminal 103, and the demultiplexer 101 filters the reception signal from the antenna terminal 103 and outputs the signal to the pair of reception terminals 107. It has a reception filter 111.

The transmission filter 109 is composed of, for example, a ladder type filter in which a plurality of resonators 37 (37S and 37P) are connected in a ladder type. That is, the transmission filter 109 includes a plurality of (or even one) series resonators 37S connected in series between the transmission terminal 105 and the antenna terminal 103, a line (series arm) thereof, and a reference potential portion 113. It has a plurality of (or even one) parallel resonators 37P (parallel arms) for connecting to and.

Each resonator 37 has a piezoelectric body 3 (not shown here), an IDT electrode 7 located on the upper surface 3a of the piezoelectric body 3, and an IDT electrode 7 located on the upper surface 3a in the propagation direction of elastic waves. It has a pair of reflectors 31 located on both sides of the.

The receiving filter 111 includes, for example, a resonator 37 and a vertically coupled multiple mode type filter 39 (hereinafter, may be referred to as an MM filter 39). The MM filter 39 is located on the piezoelectric body 3 (not shown here) and the upper surface 3a of the piezoelectric body 3, and a plurality of (three in the illustrated example) IDT electrodes 7 arranged in the propagation direction of elastic waves. And a pair of reflectors 31 arranged on both sides of an array of plurality of IDT electrodes 7.

The plurality of IDT electrodes 7 (and reflectors 31) included in the demultiplexer 101 may be provided on one piezoelectric body 3 (from another viewpoint, the substrate 23; hereinafter the same in this paragraph). It may be dispersedly provided in the above-mentioned piezoelectric body 3. For example, the plurality of resonators 37 constituting the transmission filter 109 may be provided on the same piezoelectric body 3, for example. Similarly, the resonator 37 and the MM filter 39 constituting the reception filter 111 may be provided on the same piezoelectric body 3, for example. The transmission filter 109 and the reception filter 111 may be provided on the same piezoelectric body 3 or may be provided on different piezoelectric bodies 3 from each other, for example. In addition to the above, for example, a plurality of series resonators 37S may be provided in the same piezoelectric body 3, and a plurality of parallel resonators 37P may be provided in another same piezoelectric body 3.

From another viewpoint, the device 1 having one piezoelectric body 3 may constitute the entire demultiplexer 101 or only a part of the demultiplexer 101. Further, the device 1 may constitute the entire filter (for example, the transmission filter 109 or the reception filter 111), or may constitute only a part of the filter. Further, the device 1 may simply configure the resonator 37.

The configuration of the duplexer shown in FIG. 10 is merely an example. Therefore, for example, the reception filter 111 may be configured by a ladder type filter like the transmission filter 109, or conversely, the transmission filter 109 may have the MM filter 39.

The polarization electrodes 9 may be provided in any number with respect to any one or more IDT electrodes 7 among the plurality of IDT electrodes 7 included in the demultiplexer 101. In the illustrated example, one polarization electrode 9 connected in parallel to the IDT electrode 7 of the central series resonator 37S among the three series resonators 37S is provided. Unlike the illustrated example, a polarization electrode 9 may be provided for all IDT electrodes 7. Further, even if one or more series resonators 37S, one or more parallel resonators 37P, another resonator 37, and the IDT electrode 7 of the MM filter 39 are selectively provided with one or more polarization electrodes 9. good.

One polarization electrode 9 may be connected in parallel to one IDT electrode 7 as in the third embodiment, or may be connected in parallel to two or more IDT electrodes 7 connected in series. It may have been done. With respect to the latter, for example, one polarization electrode 9 may be connected in parallel to the entire IDT electrode 7 of the two or more series resonators 37S. In the illustrated example, the polarization electrode 9 is connected in parallel to the IDT electrode 7 of one series resonator 37S. The IDT electrode 7 may be one IDT electrode 7 as shown in the figure, or may be divided into two or more IDT electrodes 7 like the three IDT electrodes 7 of the first embodiment.

In the illustrated example, the IDT electrode 7 to which the polarization electrodes 9 are connected in parallel (hereinafter, may be referred to as “first IDT electrode 7” for convenience) is directly connected to any terminal. do not have. That is, either between the antenna terminal 103 and the first IDT electrode 7, between the transmission terminal 105 and the first IDT electrode 7, and between the first IDT electrode 7 and the reference potential portion 113. Another IDT electrode 7 is interposed. Instead of the IDT electrode 7, another electronic element (for example, a resistor, a capacitor or an inductor) may be interposed between the terminal and the first IDT electrode 7.

In this way, the device 1 is connected in series between the first terminal (for example, the antenna terminal 103) and the second terminal (for example, the transmission terminal 105), or between the first terminal and the reference potential portion 113. It may have a first element and a second element (for example, two series resonators 37S on both sides of the three series resonators 37S). The first IDT electrode 7 and the polarization electrode 9 may be connected in parallel to each other between the first element and the second element.

In this case, for example, the charge of the first IDT electrode 7 does not easily escape to the terminal or the reference potential portion 113. In particular, when the first element and the second element are IDT electrodes 7 or capacitors, the first IDT electrode 7 tends to be electrically suspended and the charge is difficult to escape. As a result, the polarization direction of the first IDT electrode 7 is likely to change. By connecting the polarization electrode 9 in parallel to such a first IDT electrode 7, it is possible to efficiently reduce the change in the polarization direction in the arrangement region of the IDT electrode 7.

(Communication device)
FIG. 11 is a block diagram showing a main part of the communication device 151 as a usage example of the duplexer 101 (device 1). The communication device 151 performs wireless communication using radio waves.

In the communication device 151, the transmission information signal TIS including the information to be transmitted is modulated and the frequency is raised (converted to a high frequency signal having a carrier frequency) by RF-IC (Radio Frequency Integrated Circuit) 153, and the transmission signal TS is performed. It is said that. The transmission signal TS is amplified by the amplifier 157 and input to the demultiplexer 101 (transmission terminal 105) after the unnecessary components other than the passing band for transmission are removed by the bandpass filter 155. Then, the demultiplexer 101 (transmission filter 109) removes unnecessary components other than the passing band for transmission from the input transmission signal TS, and outputs the removed transmission signal TS from the antenna terminal 103 to the antenna 159. .. The antenna 159 converts the input electric signal (transmission signal TS) into a radio signal (radio wave) and transmits the radio signal (radio wave).

Further, in the communication device 151, the radio signal (radio wave) received by the antenna 159 is converted into an electric signal (received signal RS) by the antenna 159 and input to the demultiplexer 101 (antenna terminal 103). The demultiplexer 101 (reception filter 111) removes unnecessary components other than the passing band for reception from the input reception signal RS and outputs the signal from the reception terminal 107 to the amplifier 161. The output received signal RS is amplified by the amplifier 161 and unnecessary components other than the passing band for reception are removed by the bandpass filter 163. Then, the frequency of the received signal RS is reduced and demodulated by the RF-IC153 to obtain the received information signal RIS.

The transmission information signal TIS and the reception information signal RIS may be low frequency signals (baseband signals) including appropriate information, and are, for example, analog audio signals or digitized signals. The passing band of the radio signal may be appropriately set, and may be set to a relatively high frequency passing band (for example, 5 GHz or more). The modulation method may be phase modulation, amplitude modulation, frequency modulation, or a combination of any two or more of these. Although the direct conversion system is exemplified in FIG. 11, the circuit system may be any other appropriate circuit system, and may be, for example, a double superheterodyne system. Further, FIG. 11 schematically shows only the main part, and a low-pass filter, an isolator, or the like may be added at an appropriate position, or the position of the amplifier or the like may be changed.

The technique according to the present disclosure is not limited to the above embodiments and modifications, and may be implemented in various embodiments.

The configuration of the IDT electrode is not limited to that shown. For example, in the IDT electrode, the electrode finger of one comb tooth electrode and the electrode finger of the other comb tooth electrode are not arranged alternately one by one in the propagation direction of the elastic wave, but are arranged alternately by two. It may be what is done. Further, the IDT electrode may extend diagonally with respect to a direction orthogonal to the propagation direction of the elastic wave.

1 ... Ultrasonic device, 3 ... Piezoelectric body, 3a ... Top surface (of piezoelectric material), 5 ... Conductor layer, 7 ... IDT electrode, 9 ... Polarization electrode, 11 ... Comb tooth electrode, 13 ... Opposite electrode, G3 ... (2) Gap (of two counter electrodes).

Claims (13)

Piezoelectric and
The IDT electrode located on the upper surface of the piezoelectric body and
A polarization electrode located on the upper surface of the piezoelectric body and connected in parallel with the IDT electrode,
Have and
The polarization electrode has two counter electrodes facing each other via a gap.
The piezoelectric body is an elastic wave device in which the polarization direction in the region immediately below the gap is different from the polarization direction in the region in which the IDT electrode is arranged. The IDT electrode has a plurality of electrode fingers arranged at a predetermined pitch, and has a plurality of electrode fingers.
The elastic wave device according to claim 1, wherein the thickness of the piezoelectric body is not more than twice the pitch. It has a plurality of the IDT electrodes connected in series with each other.
The polarization electrode is connected in parallel to the entire IDT electrode.
Each of the plurality of IDT electrodes has two comb tooth electrodes that mesh with each other.
The elastic wave device according to claim 1 or 2, wherein the narrowest distance between the two counter electrodes is smaller than the total value of the narrowest distance between the two comb tooth electrodes for the plurality of IDT electrodes. The narrowest distance between the two counter electrodes is the narrowest distance between the two comb tooth electrodes, which is wider than the narrowest distance among the plurality of IDT electrodes. The described elastic wave device. It has a plurality of IDT electrodes and a plurality of reflectors adjacent to each other in the propagation direction of elastic waves.
The plurality of reflectors are connected in series with each other, and the entire plurality of reflectors are connected in parallel to the entire plurality of IDT electrodes.
Each of the plurality of reflectors has a plurality of strip electrodes extending in parallel with each other in a direction orthogonal to the propagation direction.
The elastic wave device according to claim 3 or 4, wherein one of the plurality of reflectors is the polarization electrode by dividing the plurality of strip electrodes in the orthogonal direction. The number of the IDT electrodes 7 connected in parallel with the polarization electrodes is one.
The IDT electrode has two comb tooth electrodes that mesh with each other.
The elastic wave device according to claim 1 or 2, wherein the narrowest distance between the two counter electrodes is narrower than the narrowest distance between the two comb tooth electrodes. It has one or more of the IDT electrodes and
The polarization electrode is connected in parallel to the entire IDT electrode of one or more.
The elastic wave device according to any one of claims 1 to 6, wherein the capacitance of the polarization electrode is 12% or less of the capacitance of the IDT electrode of 1 or more. The elastic wave device according to any one of claims 1 to 7, wherein the two counter electrodes face each other in only one direction. A first connection portion connecting the IDT electrode and another IDT electrode or terminal,
A second connection portion that connects the IDT electrode and the polarization electrode and has a width narrower than the width of the first connection portion.
The elastic wave device according to any one of claims 1 to 8. It has a first element and a second element connected in series between the first terminal and the second terminal, or between the first terminal and the reference potential portion.
The elastic wave device according to any one of claims 1 to 9, wherein the IDT electrode and the polarization electrode are connected in parallel between the first element and the second element. It has one or more of the IDT electrodes and
The polarization electrode is connected in parallel to the entire IDT electrode of one or more.
Each of the two comb tooth electrodes
Busbar and
A plurality of electrode fingers extending in the first direction in parallel with each other from the bus bar,
It has a dummy electrode protruding from the bus bar in the first direction between the plurality of electrode fingers.
In the two comb-tooth electrodes, the bus bars of the two comb-tooth electrodes face each other, the plurality of electrode fingers of the two comb-tooth electrodes are alternately arranged, and the plurality of electrodes of one comb-tooth electrode are arranged alternately. The tip of the finger and the tip of the dummy electrode of the other comb tooth electrode are arranged so as to face each other through the tip gap.
The narrowest portion of the gap of the polarization electrode is within the range in which the one or more IDT electrodes are located in the first direction, and the tip gap of the one or more IDT electrodes is located. The elastic wave device according to any one of claims 1 to 10, which is located outside the range. A filter having the elastic wave device according to any one of claims 1 to 11.
The antenna connected to the filter and
An integrated circuit element connected to the antenna via the filter,
Has a communication device. The method for manufacturing an elastic wave device according to any one of claims 1 to 11.
An electrode forming step of forming the IDT electrode and the polarization electrode connected in parallel to the IDT electrode on the piezoelectric body whose polarization directions are aligned over the entire surface.
After the electrode forming step, a temperature change is caused in the piezoelectric body, a voltage is applied to the two counter electrodes by the electric charge generated by the pyroelectric effect, and the polarization direction in the region directly below the gap is set to the IDT electrode. The polarization step that makes it different from the polarization direction in the region where
A method of manufacturing an elastic wave device having.

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