Elastic wave device, filter, splitter, and communication device

Abstract

To provide an elastic wave device, a filter, a splitter, and a communication device capable of at least one of converting an elastic wave into an electrical signal and converting the electrical signal into the elastic wave.SOLUTION: In an elastic wave device, a plurality of second electrode fingers 11B are connected to a potential different from that of a plurality of first electrode fingers 11A and are arranged alternately with the plurality of first electrode fingers in an elastic wave propagation (D1) direction. The elastic wave device has an intersection region R0 in which the plurality of first and second electrode fingers overlap in the D1 direction. The intersection region has a first region R1 to a fourth region R4, and the first region is located on the tip side of the plurality of first electrode fingers or the plurality of second electrode fingers in a D2 direction. The second region R2 is located closer to the center in the D2 direction than the first region R1, and has a higher sound speed than the first region. The third region is located closer to the center in the D2 direction than the second region, and has a higher sound speed than the second region. The fourth region is located closer to the center in the D2 direction than the third region, and has a higher sound speed than a third sound speed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an acoustic wave device capable of at least one of converting an acoustic wave to an electrical signal and converting an electrical signal to an acoustic wave, a filter including the acoustic wave device, a splitter including the filter, and a communication device including the splitter. [Background technology]

[0002] A known acoustic wave device has a piezoelectric layer and an IDT (Interdigital Transducer) electrode located on the piezoelectric layer (for example, see Patent Document 1 below). The IDT electrode has a pair of comb-tooth electrodes. Each comb-tooth electrode has a bus bar and a plurality of electrode fingers extending in parallel from the bus bar. The pair of comb-tooth electrodes are arranged to interdigitate with each other. A region where the electrode fingers of one comb-tooth electrode and the electrode fingers of the other comb-tooth electrode overlap in the propagation direction of the acoustic wave is called an intersection region, etc., and plays a major role in the propagation of the acoustic wave.

[0003] In Patent Document 1, the intersection region has low sound velocity regions on both sides of the direction in which the electrode fingers extend, and a high sound velocity region on the center side of the direction in which the electrode fingers extend. The sound velocity of the low sound velocity region is lower than that of the high sound velocity region. With this configuration, a so-called piston mode is utilized, and thus the spurious of the transverse mode is reduced. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-83132 Summary of the Invention

[0005] An elastic wave device according to an aspect of the present disclosure includes a piezoelectric body having a first surface and an IDT electrode located on the first surface. The IDT electrode includes a plurality of first electrode fingers and a plurality of second electrode fingers connected to a potential different from that of the plurality of first electrode fingers and arranged alternately with the plurality of first electrode fingers in an elastic wave propagation direction. An intersection region where the plurality of first electrode fingers and the plurality of second electrode fingers overlap in the elastic wave propagation direction includes a first region, a second region, and a third region. The first region is located on the tip side of the plurality of first electrode fingers. The second region is located closer to the center than the first region in the extension direction of the plurality of first electrode fingers and the plurality of second electrode fingers, and has a higher acoustic velocity than the first region. The third region is located closer to the center than the second region, and has a higher acoustic velocity than the second region.

[0006] A filter according to one embodiment of the present disclosure includes the above-described acoustic wave device and one or more other IDT electrodes located on the first surface and connected in a ladder configuration with the IDT electrode to form a ladder filter.

[0007] A filter according to one embodiment of the present disclosure includes the above-described acoustic wave device and one or more other IDT electrodes located on the first surface and aligned in the acoustic wave propagation direction with respect to the IDT electrode to form a multi-mode filter.

[0008] A duplexer according to one embodiment of the present disclosure has an antenna terminal, a transmit filter connected to the antenna terminal, and a receive filter connected to the antenna terminal, and at least one of the transmit filter and the receive filter is composed of any of the filters described above.

[0009] A communication device according to one embodiment of the present disclosure includes the above-mentioned splitter, an antenna connected to the antenna terminal, and an IC (Integrated Circuit) connected to the transmit filter and the receive filter. [Brief description of the drawings]

[0010] [Figure 1] 1 is a plan view illustrating a configuration of an elastic wave device in accordance with a first preferred embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing an example of a cross section taken along line II-II in FIG. [Diagram 3] 2 is a diagram showing another example of a cross section taken along line II-II in FIG. 1. [Figure 4] 10 is a plan view illustrating a configuration of an elastic wave device according to a second preferred embodiment of the present invention. FIG. [Diagram 5] 5 is a cross-sectional view taken along line VV in FIG. 4. [Figure 6] 11 is a plan view illustrating a configuration of an elastic wave device according to a third preferred embodiment of the present invention. FIG. [Figure 7] 1 is a plan view illustrating a configuration of an elastic wave resonator according to a preferred embodiment of the present invention. [Figure 8] 1 is a circuit diagram illustrating a configuration of a duplexer according to an embodiment of the present invention. [Figure 9] 1 is a block diagram showing a configuration of a communication device according to an embodiment. [Figure 10] FIG. 4 is a diagram showing characteristics of the resonators according to the first comparative example and the first embodiment. [Figure 11] FIG. 11 is a diagram showing characteristics of the resonators according to the second comparative example and the first embodiment. [Figure 12] 5 is a diagram showing the characteristics of the resonators according to the first and second comparative examples and the second embodiment. FIG. [Figure 13] 11 is a diagram showing the characteristics of the resonators according to the first and second comparative examples and the third embodiment. FIG. [Figure 14] FIG. 11 is a diagram showing the characteristics of the resonators according to the fourth to seventh embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings. The drawings used in the following description are schematic. Therefore, for example, the dimensional ratios in the drawings do not necessarily match the actual ones. The dimensional ratios may not match between drawings. Certain shapes or dimensions may be shown exaggerated.

[0012] In the elastic wave device according to the present disclosure, any direction may be upward or downward. However, in the following, for convenience, an orthogonal coordinate system consisting of the D1 axis, the D2 axis, and the D3 axis is defined, and terms such as upper surface and lower surface may be used with the positive side of the D3 axis being upward. In addition, when referring to a plan view or a plan perspective view, unless otherwise specified, it refers to a view in the D3 direction. Note that the D1 axis is defined to be parallel to the propagation direction of an elastic wave propagating along the upper surface of a piezoelectric body described later, the D2 axis is defined to be parallel to the upper surface of the piezoelectric body and perpendicular to the D1 axis, and the D3 axis is defined to be perpendicular to the upper surface of the piezoelectric body.

[0013] Regarding the embodiments described after the first embodiment, basically, only the differences from the previously described embodiment will be described. Matters not specifically mentioned may be considered to be the same as the previously described embodiment or may be inferred from the previously described embodiment.

[0014] First Embodiment (Overview of Elastic Wave Device) 1 is a plan view showing a configuration of a main part of an elastic wave device 1 (hereinafter, sometimes simply referred to as "device 1") according to a preferred embodiment of the present invention. In this figure, a velocity profile in device 1 is also shown, as will be described later.

[0015] The device 1 has, for example, a piezoelectric body 3 (see FIG. 2, etc., described later) and an IDT electrode 5 located on an upper surface 3a (an example of a first surface) of the piezoelectric body 3. FIG. 1 shows a plan view of the upper surface 3a. However, the reference numerals relating to the piezoelectric body 3 and the outer edge of the upper surface 3a are omitted from the illustration.

[0016] By applying a voltage to the IDT electrode 5, an elastic wave is excited that propagates in the crossing region R0 of the piezoelectric body 3 in the D1 direction. And / or, by the elastic wave propagating in the crossing region R0 in the D1 direction, an electric charge is generated in the piezoelectric body 3, and a voltage is applied to the IDT electrode 5. The device 1 may, for example, configure a resonator and / or a filter that utilizes such conversion between an elastic wave and a voltage (electrical signal). Note that, hereinafter, the D1 direction may be referred to as the elastic wave propagation direction or the propagation direction, etc.

[0017] On the right side of Fig. 1, a graph showing the profile of the sound speed in the device 1 is drawn. The axis parallel to the D2 direction of the graph indicates the position of the IDT electrode 5 in the D2 direction, and corresponding positions of both are connected by a dotted line. The axis parallel to the D1 direction indicates the sound speed V. On the axis, the right side of Fig. 1 (+D1 side) corresponds to the side with a higher sound speed.

[0018] Note that the graph on the right side of Fig. 1 merely shows the ranking of the sound velocities in the multiple regions. In other words, the absolute value of the sound velocity in each region, the difference in sound velocity between the multiple regions, and the ratio of sound velocities between the multiple regions are not reflected in reality. In addition, since the shape of a part of the IDT electrode 5 is exaggerated in Fig. 1, there is a contradiction between the dimensional ratio of the IDT electrode 5 and the velocity profile, as will be described later in detail.

[0019] In a typical elastic wave device, the sound velocity in the intersection region R0 is constant throughout. In an elastic wave device using a so-called piston mode, the intersection region R0 has a high sound velocity region in the center in the D2 direction and low sound velocity regions located on both sides of the high sound velocity region in the D2 direction. In other words, two regions with different sound velocities are formed in the intersection region R0.

[0020] On the other hand, in the elastic wave device 1 according to the embodiment, three or more regions with different sound velocities are formed in the intersection region R0. In the example shown in the figure, four regions, a first region R1 to a fourth region R4, are formed. This can reduce, for example, spurious responses in the transverse mode.

[0021] In the first embodiment, the regions with different sound velocities are realized by making the planar shape of the IDT electrode 5 a new one. In other words, the other configurations may be in various forms, for example, known forms. The first embodiment will be described generally in the following order. (1) Overview of IDT electrodes (Fig. 1) (2) Overview of speed profile (Fig. 1) (3) Details of the planar shape of the IDT electrodes (Fig. 1) (4) Example of dimensions of each part of the electrode fingers of an IDT electrode (described later) (Figure 1) (5) Various configuration examples of substrates containing piezoelectric bodies (Figs. 2 and 3) (6) Other configurations of the elastic wave device (7) Summary of the First Embodiment

[0022] In the above description of (1), the IDT electrode 5 may be a known embodiment, and the embodiment shown in Fig. 1 is taken as an example to describe the IDT electrode 5. However, the description may include a new embodiment unless otherwise specified. In the above description of (3), the planar shape of the IDT electrode 5 related to the velocity profile is described.

[0023] (IDT electrode overview) The IDT electrode 5 is formed of a conductor layer overlapping the upper surface 3a of the piezoelectric body 3. The IDT electrode 5 also includes a pair of comb-tooth electrodes 7. Each comb-tooth electrode 7 includes, for example, a bus bar 9 and a plurality of electrode fingers 11 extending in parallel from the bus bar 9. In the following description, the electrode fingers 11 of one comb-tooth electrode 7 (the electrode fingers 11 extending from the bus bar 9 on the -D2 side to the +D2 side in FIG. 1) may be referred to as the first electrode fingers 11A. In addition, the electrode fingers 11 of the other comb-tooth electrode 7 (the electrode fingers 11 extending from the bus bar 9 on the +D2 side to the -D2 side in FIG. 1) may be referred to as the second electrode fingers 11B.

[0024] A pair of comb-tooth electrodes 7 has a plurality of electrode fingers 11 arranged so as to interdigitate (intersect) with each other. That is, a plurality of first electrode fingers 11A and a plurality of second electrode fingers 11B are arranged alternately with one between them. In this regard, the plurality of first electrode fingers 11A and the plurality of second electrode fingers 11B may be arranged alternately one by one (as in the illustrated example), or may be arranged alternately in groups of two or more. Also, there may be unique portions due to so-called thinning out or the like. In the description of the embodiment, an example in which the electrodes are arranged alternately one by one is taken.

[0025] The busbars 9 are formed, for example, in an elongated shape that extends linearly in the elastic wave propagation direction (direction D1) with a substantially constant width. The pair of busbars 9 face each other in a direction (direction D2) perpendicular to the elastic wave propagation direction. The busbars 9 may have a variable width or may be inclined with respect to the elastic wave propagation direction.

[0026] The electrode fingers 11 have, for example, the same shape and size as one another. Each electrode finger 11 is formed, for example, in an elongated shape with its center line extending linearly in a direction (direction D2) perpendicular to the propagation direction of the elastic wave.

[0027] The multiple electrode fingers 11 are arranged in the propagation direction. When it is said that they are arranged in the propagation direction, a line (not shown) connecting the tips (or bases) of the multiple first electrode fingers 11A (or multiple second electrode fingers 11B) may be parallel to the propagation direction (as in the illustrated example), or may not be parallel. It is sufficient that adjacent electrode fingers 11 overlap in the propagation direction to form an intersection region R0.

[0028] The pitch p of the multiple electrode fingers 11 (e.g., the center-to-center distance between two adjacent electrode fingers 11) is basically constant within the IDT electrode 5. The IDT electrode 5 may have a portion that is unique in terms of the pitch p. Examples of unique portions include a narrow pitch portion where the pitch p is narrower than the majority (e.g., 80% or more), a wide pitch portion where the pitch p is wider than the majority, and a thinned-out portion where a small number of electrode fingers 11 are essentially thinned out.

[0029] In the following, unless otherwise specified, pitch p refers to the pitch of the portion excluding the above-mentioned unique portion (the majority of electrode fingers 11). In addition, in the case where the pitch varies in most of electrode fingers 11 excluding the unique portion, the average value of the pitches of most of electrode fingers 11 may be used as the value of pitch p.

[0030] The number of electrode fingers 11 may be set appropriately depending on the electrical characteristics required of IDT electrode 5 (device 1), etc. FIG. 1 is a schematic diagram, and therefore the number of electrode fingers 11 is shown to be small. In reality, more electrode fingers 11 than shown in the diagram may be arranged. For example, the number of electrode fingers 11 may be 100 or more. Note that FIG. 1 may be regarded as a diagram showing an extracted portion of IDT electrode 5.

[0031] The tip of each electrode finger 11 faces an edge of the bus bar 9 to which it is not connected, via a gap G1. The lengths of the multiple gaps G1 in the direction D2 are, for example, the same as each other.

[0032] When a voltage is applied to a pair of comb-tooth electrodes 7, the voltage is applied to the upper surface 3a of the piezoelectric body 3 by the electrode fingers 11, and the upper surface of the piezoelectric body 3 (when the piezoelectric body 3 is relatively thick) or the entire piezoelectric body 3 (when the piezoelectric body 3 is relatively thin) vibrates. This excites an elastic wave propagating along the upper surface 3a. At this time, the multiple elastic waves excited by the electrode fingers 11 are in phase with each other in a direction perpendicular to the multiple electrode fingers 11 (direction D1) when their half wavelengths are approximately equal to the pitch p, and their amplitudes are added together. That is, the elastic wave propagating in the direction D1 with the pitch p as the half wavelength is most likely to be excited. As a result, of the voltage applied to the IDT electrode 5, a component having a frequency approximately equal to the frequency of an elastic wave having a half wavelength of the pitch p is mainly converted into an elastic wave. Moreover, when an elastic wave is generated in the region of the upper surface 3a where the pair of comb-tooth electrodes 7 are arranged, the elastic wave propagating in the direction D1 is converted into a voltage with the pitch p being roughly a half wavelength, by the opposite principle to the above. Using such a principle, a resonator or a filter is realized.

[0033] As can be understood from the above description, a pair of comb-tooth electrodes 7 are connected to different potentials. First electrode finger 11A and second electrode finger 11B can be considered as electrode fingers 11 connected to different potentials.

[0034] In the device 1, an elastic wave of an appropriate mode may be used. For example, the elastic wave may be a surface acoustic wave (SAW). For example, a Rayleigh wave or a leaky wave may be used as the SAW. Furthermore, the elastic wave may be a plate wave propagating through a thin plate-like piezoelectric body. For example, an A1 mode Lamb wave, an S0 mode Lamb wave, and an SH (Shear Horizontal) type plate wave may be used as the plate wave. Furthermore, the mode of the elastic wave does not have to be clearly specified or distinguished in this way.

[0035] As described above, the pitch p of the electrode fingers 11 is basically half the wavelength of an elastic wave having a frequency equivalent to the intended resonant frequency. An example of the absolute value of the pitch p is 0.5 μm or more and 15 μm or less. The length of the electrode fingers 11 may be, for example, 10p or more or 20p or more, and may be 100p or less or 50p or less. The above lower and upper limits may be combined as appropriate.

[0036] The thickness of the IDT electrode 5 (conductor layer) is, for example, generally constant regardless of the position in the planar direction (the direction parallel to the D1-D2 plane). The thickness of the conductor layer may be set appropriately depending on the characteristics required for the device 1. For example, the thickness of the conductor layer may be 0.04p or more and 0.20p or less, and / or 50 nm or more and 600 nm or less.

[0037] The conductor layer is formed of, for example, a metal. The metal may be of any suitable type, for example, aluminum (Al) or an alloy (Al alloy) mainly composed of Al. The Al alloy is, for example, an Al-copper (Cu) alloy. The conductor layer may be composed of a plurality of metal layers. For example, the conductor layer may be composed of a relatively thin layer of titanium (Ti) overlapping the upper surface 3a of the piezoelectric body 3, and Al or an Al alloy overlapping thereon. Ti contributes to, for example, strengthening the bonding between the Al or Al alloy and the piezoelectric body 3.

[0038] (Speed ​​profile overview) In a plan view of the top surface 3a of the piezoelectric body 3, the region in which the IDT electrodes 5 are arranged can be divided into the following three regions in the direction D2 based on the configuration of the IDT electrodes 5: an intersection region R0 in which the multiple first electrode fingers 11A and the multiple second electrode fingers 11B overlap in the acoustic wave propagation direction, a gap region RG in which the gap G1 is located, and a busbar region RB in which the busbar 9 is located.

[0039] Intersection region R0 may be regarded as a region sandwiched between a line (not shown) connecting the tips of multiple first electrode fingers 11A and a line (not shown) connecting the tips of multiple second electrode fingers 11B. When a line connecting predetermined portions (e.g., tips) of multiple electrode fingers 11 is assumed, if the position of the line differs depending on which position within the width of electrode finger 11 is used as a reference, the center line of electrode finger 11 may be used as a reference.

[0040] In the illustrated example, the line connecting the tips of the first electrode fingers 11A and the line connecting the tips of the second electrode fingers 11B are parallel to each other. In other words, the intersection region R0 is a rectangle. More specifically, the line connecting the tips is perpendicular to the electrode fingers 11, and the intersection region R0 is rectangular with sides parallel to the D1 direction. The rectangle is, for example, a rectangle that is longer in the D1 direction, unlike FIG. 1. The intersection region R0 may be a shape other than a rectangle. For example, the intersection region R0 may be a parallelogram with the line connecting the tips inclined in the D1 direction.

[0041] The description of the various regions (R0, R1 to R4, RG, and RB) in this embodiment may apply to only a part of the IDT electrode in the D1 direction. For example, in the illustrated example, the line connecting the tips of the first electrode fingers 11A is linear across all of the first electrode fingers 11A. However, the line connecting the tips of the first electrode fingers 11A may be linear only for a predetermined number (e.g., 10) or more of first electrode fingers 11A. In other words, the effect of this embodiment may be obtained in only a part of the IDT electrode in the D1 direction. Therefore, for example, the various regions of the IDT electrode as a whole may extend in a V-shape in the D2 direction.

[0042] Gap region RG may be regarded as a region sandwiched between a line connecting the tips of multiple first electrode fingers 11A (or multiple second electrode fingers 11B) and an edge of bus bar 9 facing the tips of multiple first electrode fingers 11A. In the illustrated example, gap region RG is rectangular with long sides parallel to the D1 direction. However, gap region RG may be a shape other than rectangular. For example, when intersection region R0 is a parallelogram as described above, gap region RG may be a parallelogram with four sides parallel to the four sides of intersection region R0.

[0043] The busbar region RB may be regarded as a region sandwiched between an edge of the busbar 9 on the electrode finger 11 side and an edge on the opposite side. In the illustrated example, the busbar region RB is rectangular with long sides parallel to the D1 direction. However, the busbar region RB may be a shape other than rectangular. For example, when the intersection region R0 and the gap region RG are parallelogram-shaped as described above, the busbar region RB may be a parallelogram having four sides parallel to the four sides of the intersection region R0. The busbar region RB may also be a trapezoid with the side on the gap region RG side as the lower base.

[0044] As described above, the intersection region R0 has the first region R1 to the fourth region R4, which have different acoustic velocities. The acoustic velocity here may be, for example, the speed at which an elastic wave of a mode used by the device 1 propagates through the piezoelectric body 3. However, in a case where a plurality of regions are defined based on the shape of the IDT electrode 5 or the like, the magnitude relationship of the acoustic velocities of the plurality of regions is not usually reversed depending on the difference in the specific mode of the elastic wave used. Therefore, it is not necessary to specify which mode of the acoustic wave is the acoustic velocity.

[0045] The sound speed of the elastic wave is affected by the mass of the member (e.g., the IDT electrode 5) located on the upper surface 3a of the piezoelectric body 3. For example, in each region, the greater the mass per unit area, the lower the sound speed. On the other hand, when the thickness of the conductor layer constituting the IDT electrode 5 is constant, the greater the ratio of the conductor layer to the unit area, the greater the mass per unit area. Therefore, the sound speed becomes lower in regions where the area ratio of the conductor layer constituting the IDT electrode 5 is greater.

[0046] In the illustrated example, the width (length in the D1 direction) of the electrode finger 11 is not constant. As a result, a first region R1 to a fourth region R4 having different sound velocities are formed. These regions are arranged in the order of the first region R1, the second region R2, the third region R3, and the fourth region R4 from both sides of the intersection region R0 in the D2 direction toward the center. Furthermore, when these regions are listed in order from the region with the lowest sound velocity, they are the first region R1, the second region R2, the third region R3, and the fourth region R4. In other words, the sound velocity is higher in the regions closer to the center.

[0047] From another perspective, the first region R1 is located on both sides (specifically, both ends) of the intersection region R0 in the D2 direction. The second region R2 is located closer to the center of the intersection region R0 in the D2 direction than the first region R1 (specifically, adjacent to the center side of the first region R1), and has a higher sound speed than the first region R1. The third region R3 is located closer to the center of the intersection region R0 in the D2 direction than the second region R2 (specifically, adjacent to the center side of the second region R2), and has a higher sound speed than the second region R2. The fourth region R4 is located closer to the center of the intersection region R0 in the D2 direction than the third region R3 (specifically, adjacent to the center side of the second region R2 and located in the center of the intersection region R0), and has a higher sound speed than the third region R3.

[0048] In this paragraph, the line connecting the center points of the length of the intersection region R0 in the D2 direction is referred to as the center line of the intersection region R0. For example, the two first regions R1 have the same distance from the center line of the intersection region R0 (the distance from the center line in the D2 direction) and the same length in the D2 direction. The same can be said for the two second regions R2 and the two third regions R3. For example, the center of the length of the fourth region R4 in the D2 direction is located on the center line of the intersection region R0.

[0049] The third region R3 has a length (width) in the D2 direction greater than any other region in the intersection region R0. For example, the total width of the two third regions R3 may be 50% or more, 80% or more, or 90% or more of the width of the intersection region R0. The size relationship of the widths of the other regions in the intersection region R0 may be set appropriately. In the illustrated example, the largest width is the first region R1, the fourth region R4, and the second region R2.

[0050] Each of the first region R1 to the fourth region R4 is, for example, a rectangular shape having long sides parallel to the D1 direction. However, each of the first region R1 to the fourth region R4 may be a shape other than a rectangle. For example, when the intersection region R0 is a parallelogram shape as described above, each of the first region R1 to the fourth region R4 may be a parallelogram shape having four sides parallel to the four sides of the intersection region R0. For specific dimensions of the first region R1 to the fourth region R4, please refer to the details of the planar shape of the IDT electrode described later. In addition, the degree of the difference in speed between the first region R1 to the fourth region R4 may be set appropriately. For the degree of the difference in speed, please refer to the details of the planar shape of the IDT electrode that affects the speed (described later).

[0051] The busbar region RB has a lower acoustic velocity than the first region R1, in other words, a lower acoustic velocity than any region in the intersection region R0. The gap region RG has a higher acoustic velocity than, for example, the fourth region R4, in other words, a higher acoustic velocity than any region in the intersection region R0. Since the acoustic velocity in the gap region RG is higher than that in the fourth region R4, the gap region RG has a smaller area ratio occupied by the IDT electrode 5 than the fourth region R4. However, in FIG. 1 (and other figures described later), the change in width of the electrode fingers 11 is exaggerated, and as a result, the gap region RG is shown to have a larger area ratio occupied by the IDT electrode 5 than the fourth region R4, which is different from the actual area ratio.

[0052] (Details of the planar shape of the IDT electrode) Specifically, the first region R1 to the fourth region R4 (and the gap region RG) are realized by the electrode fingers 11 having the following shapes.

[0053] The width (length in the D1 direction) of the portion of electrode finger 11 located in third region R3 is referred to as the reference width. In this case, electrode finger 11 has, for example, the following portions, in order from the tip side in the longitudinal direction: tip side widened portion 11a having a width wider than the reference width; tip side main portion 11b having the reference width; narrow width portion 11c having a width narrower than the reference width; base side main portion 11d having the reference width; base side widened portion 11e having a width wider than the reference width; and base portion 11f having the reference width.

[0054] A third region R3 on the +D2 side is formed by a region where the tip side main portion 11b of the first electrode finger 11A and the root side main portion 11d of the second electrode finger 11B overlap in the propagation direction. Similarly, a third region R3 on the -D2 side is formed by a region where the root side main portion 11d of the first electrode finger 11A and the tip side main portion 11b of the second electrode finger 11B overlap in the propagation direction.

[0055] A first region R1 on the +D2 side is formed by a region where the tip side widened portion 11a of the first electrode finger 11A and the base side widened portion 11e of the second electrode finger 11B overlap in the propagation direction. Similarly, a first region R1 on the -D2 side is formed by a region where the base side widened portion 11e of the first electrode finger 11A and the tip side widened portion 11a of the second electrode finger 11B overlap in the propagation direction.

[0056] As described above, in the third region R3, main portions having the standard width overlap each other, whereas in the first region R1, widened portions having a width larger than the standard width overlap each other. As a result, the area ratio of the IDT electrode 5 in the first region R1 is larger than that in the third region R3. As a result, the sound speed in the first region R1 is lower than that in the third region R3.

[0057] The base-side widened portion 11e of the second electrode finger 11B extends further toward the -D2 side (the center side of the intersection region R0) than the tip-side widened portion 11a of the first electrode finger 11A. As a result, the base-side widened portion 11e of the second electrode finger 11B overlaps not only the tip-side widened portion 11a of the first electrode finger 11A but also a part of the tip-side main portion 11b of the first electrode finger 11A in the propagation direction. The region where the base-side widened portion 11e and the tip-side main portion 11b overlap forms the second region R2 on the +D2 side. Note that the position of the end of the tip-side widened portion 11a of the first electrode finger 11A on the +D2 side and the position of the end of the base-side widened portion 11e of the second electrode finger 11B on the +D2 side are, for example, roughly aligned.

[0058] Similarly, the base-side widened portion 11e of the first electrode finger 11A extends further toward the +D2 side (the center side of the intersection region R0) than the tip-side widened portion 11a of the second electrode finger 11B. As a result, the base-side widened portion 11e of the first electrode finger 11A overlaps not only the tip-side widened portion 11a of the second electrode finger 11B but also a part of the tip-side main portion 11b of the second electrode finger 11B in the propagation direction. The region where the base-side widened portion 11e and the tip-side main portion 11b overlap constitutes the second region R2 on the -D2 side. Note that the position of the end of the tip-side widened portion 11a of the second electrode finger 11B on the -D2 side and the position of the end of the base-side widened portion 11e of the first electrode finger 11A on the -D2 side are, for example, roughly aligned.

[0059] As described above, in the third region R3, the main portions having the reference width overlap in the propagation direction. In the first region R1, the widened portions having a width larger than the reference width overlap in the propagation direction. On the other hand, in the second region R2, the main portions and the widened portions overlap in the propagation direction. As a result, the area ratio of the IDT electrode 5 in the second region R2 is smaller than that in the first region R1, and the area ratio of the IDT electrode 5 in the second region R2 is larger than that in the third region R3. As a result, the sound speed in the second region R2 is higher than that in the first region R1, and lower than that in the third region R3.

[0060] The fourth region R4 is formed by a region where the narrow portion 11c of the first electrode finger 11A and the narrow portion 11c of the second electrode finger 11B overlap in the propagation direction. In the third region R3, main portions having the reference width overlap, whereas in the fourth region R4, narrow portions 11c having a width narrower than the reference width overlap. Therefore, the area ratio of the IDT electrode 5 in the fourth region R4 is smaller than that in the third region R3. As a result, the sound speed in the fourth region R4 is higher than that in the third region R3.

[0061] In the gap region RG, the gap G1 on the tip side of the first electrode finger 11A and the root portion 11f of the second electrode finger 11B overlap in the propagation direction. In FIG. 1, the narrow portion 11c is exaggerated to be narrower than the main portion, but in reality, the narrow portion 11c is larger than 1 / 2 the width of the root portion 11f (reference width in the illustrated example). As described above, in the fourth region R4, the narrow portions 11c overlap in the propagation direction. Therefore, the area ratio of the IDT electrode 5 in the gap region RG is smaller than that in the fourth region R4. Thus, the gap region RG has a higher sound velocity than the fourth region R4 (and the first region R1 to the third region R3). However, unlike the illustrated velocity profile, the gap region RG may have a lower sound velocity than the fourth region R4.

[0062] In the busbar region RB, the busbar 9 extends in the D1 direction, so that the area ratio of the IDT electrode 5 to the busbar region RB is 100%. On the other hand, in various regions between a pair of busbars 9, the first electrode finger 11A and the second electrode finger 11B are separated from each other, so that the area ratio of the IDT electrode 5 is less than 100%. Therefore, the sound speed in the busbar region RB is lower than that in any other region within the region in which the IDT electrode 5 is arranged.

[0063] For example, a busbar may have a plurality of openings arranged in the D1 direction. In this case, the area ratio of the IDT electrode in the busbar region is not 100%, and the sound speed in the busbar region becomes high. However, this can be considered as a problem of which parts of the IDT electrode are defined as the busbar and the busbar region. For example, in a busbar having a plurality of openings as described above, the part located on the intersection region R0 side of the plurality of openings may be considered as the busbar 9 according to the embodiment.

[0064] Each of the multiple portions (11a to 11f) of the electrode finger 11 extends, for example, with a constant width (in the D1 direction), and thus a step is formed at the boundary between adjacent portions. More specifically, the step has, for example, a relatively short edge extending generally parallel to the D1 direction. From another perspective, the speed profile shows a step-like change in speed. Note that in reality, the corners of the step may be rounded or the short edge may be curved due to processing errors or the like.

[0065] Unlike the illustrated example, at least one of the multiple parts (11a-11f) may have a portion that extends with a constant width, and the width of the portion that is connected to the adjacent part may vary so that the step is gentle. In other words, when the existence of multiple parts (11a-11f) is clear from the portion that extends with a constant width, the boundary between adjacent parts does not necessarily have to be clear. From another perspective, when the existence of multiple regions (R1-R4) is clear from the range (direction D2) where the speed is constant in the speed profile, the boundary between adjacent regions does not necessarily have to be clear.

[0066] Also, unlike the illustrated example, a step or a bend in the side edge of electrode finger 11 may be formed at the boundary between adjacent portions among the plurality of portions (11a to 11f) as in the illustrated example, and the width of at least one of the adjacent portions may vary over the entire length of the portion. In other words, when the boundary between adjacent portions is clear and the existence of the plurality of portions (11a to 11f) is obvious, each portion may not have a portion that extends with a constant width. From another perspective, when the boundary between adjacent regions is clear in the velocity profile due to a step or bend in the line indicating the velocity, and thus the existence of the plurality of regions (R1 to R4) is obvious, each region may not have a range (direction D2) where the velocity is constant.

[0067] (Example of dimensions of each part of the electrode finger) Specific dimensions of each portion (11a to 11f) of electrode finger 11 may be set appropriately. For example, they are as follows. In the following, the ratio (=width / 2p) of the width (in the D1 direction) of electrode finger 11 to twice the pitch p of electrode finger 11 (2p) may be referred to as the duty ratio.

[0068] The tip side main portion 11b and the root side main portion 11d account for most of the length (D2 direction) of the electrode finger 11. For example, the total length of the tip side main portion 11b and the root side main portion 11d may account for 50% or more, 80% or more, or 90% or more of the length of the electrode finger 11 (or the length of the intersection region R0 in the D2 direction). The lengths of the tip side main portion 11b and the root side main portion 11d are approximately equal. However, the root side main portion 11d is shorter than the tip side main portion 11b by the amount that the root side widened portion 11e is longer than the tip side widened portion 11a.

[0069] In the illustrated example and in an embodiment different from the illustrated example (for example, an embodiment in which the fourth region R4 is not formed), the above term "the total length of the tip side main portion 11b and the root side main portion 11d" may be replaced with the term "the length of the portion having the reference width in the intersection region R0." The length of the tip side main portion 11b and / or the root side main portion 11d may be determined as a result of setting the entire length of the electrode finger 11 (or the length of the intersection region R0 in the D2 direction) and the length of other portions of the electrode finger 11.

[0070] The width of the tip side main portion 11b and the width of the base side main portion 11d are the same and are the standard widths as described above. The duty ratio of the standard width may be, for example, 0.40 or more or 0.45 or more, and may be 0.60 or less or 0.55 or less. The above upper and lower limits may be appropriately combined.

[0071] The length of the tip-side widened portion 11a (in the D2 direction, in other words, the width of the first region R1) may be, for example, 0.5p or more, 1.0p or more, or 1.5p or more, and may be 4.0p or less, 3.0p or less, or 2.5p or less. The above upper and lower limits may be combined as appropriate.

[0072] The difference between the length (D2 direction) of the base side widening portion 11e and the length of the tip side widening portion 11a (in other words, the width of the second region R2) may be, for example, 0.1p or more or 0.3p or more, and may be 1p or less or 0.7p or less. The above upper and lower limits may be appropriately combined. From another perspective, the width of the second region R2 may be, for example, 0.1 times or more or 0.2 times or more the width of the first region R1, and may be less than 1 time, 0.5 times or less, or 0.3 times or less the width of the first region R1. The above upper and lower limits may be appropriately combined. In the above, the width of the second region R2 is exemplified as being less than the width of the first region R1, but the width of the second region R2 may be greater than or equal to the width of the first region R1.

[0073] The width (D1 direction) of the tip side widening portion 11a and the width of the base side widening portion 11e are, for example, the same as each other. However, the two may be different. The duty ratio of the width of these widening portions may be, for example, 0.50 or more, 0.55 or more, or 0.60 or more, and may be 0.80 or less, 0.75 or less, or 0.70 or less, provided that it is greater than the duty ratio of the reference width. The above upper and lower limits may be combined as appropriate. From another perspective, the width of the widening portion may be, for example, 1.1 times or more, 1.2 times or more, or 1.5 times or less, or 1.4 times or less, of the reference width. The above upper and lower limits may be combined as appropriate.

[0074] The length of the narrow portion 11c (in the D2 direction; in other words, the width of the fourth region R4) may be, for example, 0.2p or more, 0.5p or more, or 0.7p or more, and may be less than 3.0p, 1.5p, or 1.0p. The above upper and lower limits may be combined as appropriate.

[0075] The duty ratio of the width (D1 direction) of the narrow width portion 11c may be, for example, 0.10 or more, 0.30 or more, or 0.35 or more, and may be 0.50 or less, or 0.45 or less, provided that it is smaller than the duty ratio of the reference width. The upper and lower limits may be combined as appropriate. From another perspective, the width of the narrow width portion 11c may be, for example, 0.50 times or more, 0.70 times or more, or 0.75 times or more of the reference width, and may be 0.95 times or less, 0.90 times or less, or 0.85 times or less of the reference width. The upper and lower limits may be combined as appropriate.

[0076] The length of the base portion 11f (in the D2 direction; in other words, the width of the gap region RG) may be, for example, 0.1p or more, 0.2p or more, or 0.3p or more, and may be 1.0p or less, 0.7p or less, or 0.5p or less. The above upper and lower limits may be appropriately combined.

[0077] The width (D1 direction) of the root portion 11f is, for example, the standard width (in other words, the same as the width of the main portion) as described above. However, the width of the root portion 11f may be smaller or larger than the standard width. For example, the width of the root portion 11f may be the same as the width of the root side widened portion 11e. In this case, it may be considered that the root side widened portion 11e extends to the bus bar 9.

[0078] (Various configuration examples of substrates including piezoelectric bodies) The piezoelectric body 3 having the upper surface 3a on which the IDT electrode 5 is formed may be, for example, a part or the whole of a substrate. The substrate may have various configurations, for example, a known configuration. The following are examples of the substrate configuration.

[0079] 2 is a cross-sectional view showing the configuration of a substrate 13A as a first example of the substrate, the cross section corresponding to the cross section taken along line II-II in FIG.

[0080] Substrate 13A has, for example, support substrate 15, intermediate layer 17 overlapping the upper surface of support substrate 15, and piezoelectric body 3 overlapping the upper surface of intermediate layer 17. Here, piezoelectric body 3 is configured as a piezoelectric film. In the description of the configuration of the elastic wave device, the terms "plate," "layer," and "film" are used interchangeably unless otherwise specified. The thickness of each layer is constant, for example, regardless of the position in the planar direction (direction parallel to the D1-D2 plane).

[0081] The piezoelectric body 3 is made of, for example, a single crystal having piezoelectricity. Examples of materials constituting such a single crystal include lithium tantalate (LiTaO3, hereinafter sometimes abbreviated as LT), lithium niobate (LiNbO3, hereinafter sometimes abbreviated as LN), and quartz (SiO2). The piezoelectric body 3 may be made of polycrystal. The cut angle, planar shape, and various dimensions of the piezoelectric body 3 may be set appropriately. For example, a piezoelectric body made of LT or LN may be a rotated Y-cut X-propagation type. That is, the propagation direction of the elastic wave (D1 direction) and the X-axis may be approximately the same (for example, the difference between the two is ±10°). In this case, the inclination angle of the Y-axis with respect to the normal line (D3 direction) of the upper surface 3a of the piezoelectric body 3 may be set appropriately. The thickness of the piezoelectric body 3 may be, for example, 0.1p or more or 0.3p or more, and may be 2p or less or 1p or less. The upper and lower limits may be combined appropriately.

[0082] The support substrate 15 may contribute to at least one of improving the strength of the substrate 13A, compensating for changes in characteristics caused by temperature changes (temperature compensation), and confining elastic waves in the piezoelectric body 3. The improvement in strength may be achieved, for example, by appropriately setting the thickness of the support substrate 15 made of a material having a certain degree of strength. The temperature compensation may be achieved, for example, by making the linear expansion coefficient of the support substrate 15 smaller than the linear expansion coefficient of the piezoelectric body 3. The confinement of elastic waves may be achieved, for example, by making the sound velocity of the support substrate 15 higher than the sound velocity of the piezoelectric body 3 (and / or the intermediate layer 17) and / or by making the acoustic impedance of the support substrate 15 different from the acoustic impedance of the intermediate layer 17.

[0083] The material and thickness of the support substrate 15 may be appropriately set in light of the above-mentioned purpose. For example, the material of the support substrate 15 may be a semiconductor such as silicon (Si), a single crystal such as sapphire (Al2O3), or a ceramic such as aluminum oxide sintered body (Al2O3). The thickness of the support substrate 15 is, for example, 1p or more or 3p or more. In addition, the thickness of the support substrate 15 is, for example, thicker than the thickness of the piezoelectric body 3.

[0084] The intermediate layer 17 may contribute to at least one of, for example, improving the bonding strength between the piezoelectric body 3 and the support substrate 15 and confining elastic waves in the piezoelectric body 3. The improvement of the bonding strength may be achieved, for example, by selecting, as the material of the intermediate layer 17, a material that has a relatively high bonding strength between the piezoelectric body 3 and the support substrate 15 when a predetermined bonding method is used. The confinement of elastic waves may be achieved, for example, by the sound velocity of the intermediate layer 17 being lower than the sound velocity of the piezoelectric body 3 (and / or the support substrate 15) and / or by the acoustic impedance of the intermediate layer 17 being different from the acoustic impedance of the piezoelectric body 3 (and / or the support substrate 15).

[0085] The material and thickness of the intermediate layer 17 may be appropriately set in light of the above-mentioned purpose. For example, the material of the intermediate layer 17 may be silicon oxide (SiO2). The thickness of the intermediate layer 17 may be, for example, 0.01p or more or 0.1p or more, and may be 2p or less, 1p or less, or 0.5p or less. The above upper and lower limits may be appropriately combined. In addition, the thickness of the intermediate layer 17 is, for example, thinner than the thickness of the support substrate 15. In addition, the thickness of the intermediate layer 17 may be thinner, equal to, or thicker than the thickness of the piezoelectric body 3.

[0086] As described above, the intermediate layer 17 may be a low acoustic velocity layer having a lower acoustic velocity than the piezoelectric body 3, while the support substrate 15 may be a high acoustic velocity layer having a higher acoustic velocity than the piezoelectric body 3. This can reduce, for example, elastic waves leaking from the piezoelectric body 3.

[0087] The sound velocity here may be, for example, a shear wave sound velocity determined by the physical properties of each material itself. In other words, unlike the sound velocities that distinguish the first region R1 to the fourth region R4 described above, the influence of the IDT electrode 5 may be ignored. The shear wave sound velocity is obtained by the square root of the value obtained by dividing the elastic modulus by the density. However, the sound velocity of the piezoelectric body 3 compared with the sound velocity of the intermediate layer 17 and the support substrate 15 may be the sound velocity of the elastic wave in the third region R3 of the mode to be used, instead of the shear wave sound velocity. In addition, the sound velocity of the intermediate layer 17 and / or the support substrate 15 may be the sound velocity of the bulk wave of the mode that has a relatively large effect on the leakage of the energy of the elastic wave of the mode to be used.

[0088] The material of the intermediate layer 17 as the low acoustic velocity layer and the material of the support substrate 15 as the high acoustic velocity layer may be combined arbitrarily. For example, the combination of these materials may be the above-mentioned combination of SiO2 and Si. When the intermediate layer 17 is provided as the low acoustic velocity layer, a layer for improving the bonding strength between the intermediate layer 17 and the piezoelectric body 3 and / or a relatively thin layer for improving the bonding strength between the intermediate layer 17 and the support substrate 15 may be provided.

[0089] 3 is a cross-sectional view showing the configuration of a substrate 13B as a second example of the substrate, the cross section corresponding to the cross section taken along line II-II in FIG.

[0090] The substrate 13B is the substrate 13A described above, but with a multilayer film 19 instead of the intermediate layer 17. The multilayer film 19 has two or more layers (six layers in the illustrated example) of acoustic films (first film 21A and second film 21B). The materials of the acoustic films adjacent to each other in the stacking direction (overlapping each other without any other acoustic film in between) are different from each other. From another point of view, the acoustic impedances of the adjacent acoustic films are different from each other. This makes the reflectance of the elastic wave relatively high at the interface between the two, for example. As a result, for example, the leakage of the elastic wave propagating through the piezoelectric body 3 is reduced. The combination of the intermediate layer 17 and the support substrate 15 in the substrate 13A in FIG. 2 may be regarded as a kind of multilayer film. In the substrate 13B in FIG. 3, the multilayer film may be defined to include the support substrate 15.

[0091] The number of types of materials of the acoustic membranes of the multilayer film 19 and the number of the acoustic membranes may be set appropriately. In the illustrated example, two types of acoustic membranes (first membrane 21A and second membrane 21B) are alternately laminated in three or more layers (more specifically, six layers). The material of the acoustic membrane is also arbitrary. For example, the material of the first membrane 21A may be silicon dioxide (SiO2). The material of the second membrane 21B may be tantalum pentoxide (Ta2O5), hafnium oxide (HfO2), zirconium dioxide (ZrO2), titanium oxide (TiO2), magnesium oxide (MgO) or silicon nitride (Si3N4). In this case, the first membrane 21A has, for example, a lower acoustic impedance than the second membrane 21B. The thickness of the acoustic membrane may be set appropriately, and for example, the explanation of the thickness of the intermediate layer 17 above may be used.

[0092] The acoustic films (first film 21A and second film 21B) may be configured with a low acoustic velocity film and a high acoustic velocity film, similar to the intermediate layer 17 and support substrate 15 of the substrate 3A in Fig. 2. For example, the first film 21A may be made of a material having a lower acoustic velocity than the piezoelectric body 3 (e.g., SiO2 or Ta2O5). The second film 21B may be made of a material having a higher acoustic velocity than the piezoelectric body 3 (e.g., Si3N4).

[0093] Although not particularly shown, the substrate including the piezoelectric body 3 may be in various forms other than the above examples. For example, the substrate may be substantially entirely composed of the piezoelectric body 3. From another point of view, the piezoelectric body 3 may be relatively thick. The substrate may have a cavity below the relatively thin (for example, 2p or less or 1p or less) piezoelectric body 3. The substrate may have a high acoustic velocity layer overlapping the lower surface of the intermediate layer 17 as the low acoustic velocity layer, separate from the support substrate 15, in the substrate 13A of FIG. 2. Contrary to the explanation of the substrates 13A and 13B, the high acoustic velocity layer may overlap the lower surface of the piezoelectric body 3 to realize the confinement of the elastic wave.

[0094] (Other Configurations of Elastic Wave Device) Although not shown, the acoustic wave device 1 may have an insulating protective film that covers the upper surface 3a of the piezoelectric body 3 from above the conductor layer including the IDT electrode 5. The protective film may contribute to reducing corrosion of the conductor layer and / or contribute to temperature compensation, for example. Examples of materials for the protective film include SiO2, Si3N4, and Si. The protective film may be a laminate of these materials.

[0095] Furthermore, the device 1 may have an additional film overlapping the upper or lower surface of the IDT electrode 5. The additional film, for example, overlaps the entire or part of the IDT electrode 5 and has a shape that fits within the IDT electrode 5 in a planar perspective view. Such an additional film is made of, for example, an insulating material or a metal material that has acoustic properties different from those of the material of the IDT electrode 5, and contributes to improving the reflection coefficient of the acoustic wave.

[0096] The device 1 may be packaged as appropriate. Examples of package configurations include the following: A package in which the substrate 13A (or 13B, etc.) is mounted on a substrate (not shown) with a gap between them so that the top surface 3a of the piezoelectric element 3 faces the substrate, and then sealed with molding resin from above; or a wafer-level package in which a box-shaped cover that covers the top surface 3a is provided on the substrate 13A (or 13B, etc.).

[0097] (Summary of the first embodiment) As described above, the acoustic wave device 1 includes a piezoelectric body 3 and an IDT electrode 5. The piezoelectric body 3 includes a first surface (upper surface 3a). The IDT electrode 5 is located on the upper surface 3a. The IDT electrode 5 includes a plurality of first electrode fingers 11A and a plurality of second electrode fingers 11B. The plurality of second electrode fingers 11B are connected to a potential different from that of the plurality of first electrode fingers 11A and are arranged alternately with the plurality of first electrode fingers 11A in the acoustic wave propagation direction (direction D1). The device 1 includes an intersection region R0 in which the plurality of first electrode fingers 11A and the plurality of second electrode fingers 11B overlap with each other in the acoustic wave propagation direction. The intersection region R0 includes a first region R1 to a third region R3 (here, the region on the +D2 side is taken as an example). The first region R1 is located on the tip side of the plurality of first electrode fingers 11A. The second region R2 is located closer to the center than the first region R1 in the direction (D2 direction) in which the first electrode fingers 11A and the second electrode fingers 11B extend, and has a higher acoustic velocity than the first region R1. The third region R3 is located closer to the center than the second region R2, and has a higher acoustic velocity than the second region R2.

[0098] Therefore, for example, spurious can be reduced. Specifically, for example, by configuring the first region R1 with a slow sound speed at the end side of the D2 direction of the intersection region R0, a piston mode (or a mode similar thereto; the same applies below) can be used. As a result, spurious of the transverse mode can be reduced. Furthermore, by configuring the second region R2 with a higher sound speed than the first region R1 and a lower sound speed than the third region R3, spurious can be further reduced. The applicant has confirmed this effect by actual measurements and simulation calculations of a prototype, and will show some examples later. The reason why spurious is reduced by forming the second region R2 is, for example, that the effect of reducing spurious of the transverse mode is enhanced by configuring a double low sound speed region that contributes to realizing the piston mode.

[0099] The widths (reference widths) of the multiple first electrode fingers 11A and the multiple second electrode fingers 11B in the third region R3 are compared. In this case, the first region R1 may have widened portions in both the multiple first electrode fingers 11A and the multiple second electrode fingers 11B (in the first region R1 on the +D2 side, the tip side widened portion 11a of the first electrode finger 11A and the base side widened portion 11e of the second electrode finger 11B). The second region R2 may have the widened portion in either the multiple first electrode fingers 11A or the multiple second electrode fingers 11B (the second electrode finger 11B in the second region R2 on the +D2 side), but may not have the widened portion in the other of the multiple first electrode fingers 11A and the multiple second electrode fingers 11B (the first electrode finger 11A in the second region R2 on the +D2 side).

[0100] In this case, for example, the end of the tip-side widened portion 11a of the first electrode finger 11A on the -D2 side and the end of the base-side widened portion e of the second electrode finger 11B on the -D2 side are different from each other in the D2 direction. As a result, the reflection position and / or diffraction position of the elastic wave propagating in the lateral direction differs depending on the position in the D1 direction. In addition, the probability that the elastic waves in the lateral direction reinforce each other is reduced, and spurious is reduced. In addition, for example, it is easy to realize the second region R2 having a higher acoustic velocity than the first region R1 and a lower acoustic velocity than the third region R3. More specifically, for example, it is as follows. As an aspect different from the present embodiment, an aspect in which the width of the electrode finger 11 in the second region R2 is set to a size between the width of the electrode finger 11 in the first region R1 and the width of the electrode finger 11 in the third region R3 (this aspect is also included in the technology according to the present disclosure) is considered. In this embodiment, it may be difficult to realize such a width of the second region R2 due to the processing accuracy of the width of the electrode finger 11. However, in this embodiment, the second region R2 can be realized even in such a case.

[0101] The widened portions (tip side widened portion 11a) located on the tip side of the multiple first electrode fingers 11A may be located in the first region R1 on the +D2 side, and may not be located in the second region R2 on the +D2 side. The widened portions (root side widened portion 11e) located on the root side of the multiple second electrode fingers 11B may be located in the first region R1 on the +D2 side and the second region R2 on the +D2 side. In other words, the root side widened portion 11e may extend closer to the center in the D2 direction of the intersection region R0 than the tip side widened portion 11a.

[0102] In this case, for example, compared to an embodiment in which tip side widened portion 11a extends toward the center of intersection region R0 in direction D2 further than base side widened portion 11e (this embodiment may also be included in the technology according to the present disclosure), it is easier to ensure the cross-sectional area of ​​electrode fingers 11 on the bus bar 9 side. As a result, signal and / or heat transfer between bus bar 9 and electrode fingers 11 is facilitated.

[0103] The elastic wave device 1 may further include a fourth region R4. The fourth region R4 may be located closer to the center in direction D2 than the third region R3, and may have a higher sound speed than the third region R3.

[0104] In this case, for example, spurious can be further reduced. The applicant has confirmed this effect by actual measurements of a prototype and simulation calculations, and will provide some examples later. The reason why spurious is reduced by forming the fourth region R4 is, for example, that the effect of reducing spurious in the transverse mode is enhanced by the multiplexing of the velocity profile that contributes to the realization of the piston mode.

[0105] The length (width) of the fourth region R4 in the direction (direction D2) in which the multiple first electrode fingers 11A and the multiple second electrode fingers 11B extend may be less than 1.5 times the pitch p of the multiple first electrode fingers 11A and the multiple second electrode fingers 11B.

[0106] In this case, for example, the characteristics of the elastic wave device 1 are improved. The applicant has confirmed this effect through actual measurements of a prototype and simulation calculations, and will provide some examples later. One reason for the improved characteristics when the width of the fourth region R4 is less than 1.5p is that, for example, the short width of the fourth region R4 makes it easier to ensure the width of the third region R3, which is responsible for basic characteristics. Another reason is that, for example, transverse mode elastic waves having a wavelength (2p) equivalent to that of the elastic waves intended to be used do not fit within the fourth region R4.

[0107] The acoustic wave device 1 may further include a low acoustic velocity film (intermediate layer 17 in FIG. 2 or first film 21A in FIG. 3) and a high acoustic velocity film (support substrate 15 in FIG. 2 or second film 21B in FIG. 3). The low acoustic velocity film overlaps the side opposite to the top surface 3a of the piezoelectric body 3 made of a piezoelectric film, and has a lower acoustic velocity than the piezoelectric body 3. The high acoustic velocity film overlaps the side opposite to the low acoustic velocity film and the piezoelectric body 3, and has a higher acoustic velocity than the piezoelectric body 3.

[0108] In this case, for example, it is possible to reduce the elastic waves leaking from the piezoelectric body 3. As a result, the characteristics of the device 1 are improved.

[0109] <Second embodiment> Fig. 4 is a plan view illustrating a configuration of an elastic wave device 201 (hereinafter, sometimes referred to as "device 201") according to a second embodiment. Fig. 5 is a cross-sectional view taken along line VV in Fig. 4.

[0110] For convenience, the upper surfaces (i.e., surfaces other than the cross sections) of the first additional film 23A and the second additional film 23B described below are hatched in Fig. 4. Also, for convenience, some of the reference numerals relating to the IDT electrode 205 are attached to portions that are covered by the additional films and are not visible in Fig. 4. Note that, unlike the following description, the additional films may be regarded as a part of the IDT electrode 205.

[0111] In the explanation of the first embodiment, it has been stated that the sound velocity of an elastic wave is affected by the mass of a member (e.g., the IDT electrode 5) located on the upper surface 3a of the piezoelectric body 3. In the first embodiment, the width of the electrode fingers 11 is changed to make the masses on the upper surface 3a in the first region R1 to the fourth region R4 different from one another, thereby realizing the velocity profile in FIG. 1. In the second embodiment, the width of the electrode fingers 11 is not changed, but additional films (first additional film 23A and second additional film 23B) are provided to partially overlap the electrode fingers 11, thereby realizing the velocity profile in FIG. 1. More specifically, this is as follows.

[0112] The IDT electrode 205 has a pair of comb-tooth electrodes 207, similar to the IDT electrode 5 of the first embodiment. The pair of comb-tooth electrodes 207 has a bus bar 9 and a plurality of electrode fingers 211 (a plurality of first electrode fingers 211A and a plurality of second electrode fingers 211B). However, unlike the plurality of electrode fingers 11 of the first embodiment, the plurality of electrode fingers 211 extend with a constant width over their entire length.

[0113] A first additional film 23A and a second additional film 23B are overlapped in this order on the IDT electrode 205. The first additional film 23A overlaps portions of the electrode finger 211 that correspond to the tip side widened portion 11a, the tip side main portion 11b, the base side main portion 11d, and the base side widened portion 11e of the electrode finger 11 of the first embodiment. The second additional film 23B overlaps portions of the electrode finger 211 that correspond to the tip side widened portion 11a and the base side widened portion 11e of the electrode finger 11 of the first embodiment. As a result, the first region R1 to the fourth region R4 having the same velocity profile as the velocity profile of FIG. 1 are realized, as in the first embodiment.

[0114] In the illustrated example, the first additional film 23A and the second additional film 23B overlap a portion of the electrode finger 211 that corresponds to the root portion 11f of the electrode finger 11 in the first embodiment. This corresponds to the fact that the width of the root portion 11f is set to be equal to the width of the base-side widened portion 11e in the first embodiment. However, just as the width of the root portion 11f is arbitrary, the first additional film 23A and / or the second additional film 23B may not be provided in the portion that corresponds to the root portion 11f.

[0115] In the illustrated example, the first additional film 23A and the second additional film 23B overlap the busbar 9. Unlike the illustrated example, the first additional film 23A and / or the second additional film 23B may not overlap the busbar 9. The presence or absence of the first additional film 23A and the second additional film 23B in the portions corresponding to the busbar 9 and the root portion 11f may be set so that the sound velocity in the busbar region RB is lower than the sound velocity in the gap region RG.

[0116] The additional film was mentioned in the description of the first embodiment. The description of the additional film in the first embodiment may be applied to this embodiment. For example, unlike the illustrated example, the additional film may be located on the lower surface of the IDT electrode 5. The specific material and thickness of the additional film are arbitrary. For example, examples of the additional film material that is an insulating material include Ta2O5, TaSi2, W5Si2, WC, and TiN. The thickness of the additional film may be, for example, 0.01p or more and 0.2p or less.

[0117] As described above, in the present embodiment, the intersection region R0 of the elastic wave device 201 includes the first region R1 to the third region R3. Therefore, the same effects as those of the first embodiment can be achieved. For example, spurious emissions can be reduced.

[0118] As shown in this embodiment, the first region R1 on the +D2 side may have an additional film (second additional film 23B) overlapping both the multiple first electrode fingers 211A and the multiple second electrode fingers 211B. The second region R2 on the +D2 side may have the second additional film 23B overlapping either one of the multiple first electrode fingers 211A and the multiple second electrode fingers 211B (the second electrode fingers 211B), and may not have the second additional film 23B overlapping the other (the first electrode finger 211A). The third region R3 may not have the second additional film 23B overlapping either the multiple first electrode fingers 211A or the multiple second electrode fingers 211B.

[0119] In this manner, in an aspect in which the additional film is used to realize regions with different sound velocities, the likelihood of short-circuiting due to widening of the electrode fingers 11 and / or an increase in resistance due to narrowing of the electrode fingers 11 is reduced. As a result, for example, it is easy to increase the difference in sound velocities between the regions. In addition, since the first embodiment does not have an additional film compared to the second embodiment, the number of types of materials required can be reduced and the manufacturing process can be simplified. As a result, costs can be reduced.

[0120] <Third embodiment> FIG. 6 is a plan view showing a configuration of an elastic wave device 301 (hereinafter, sometimes simply referred to as "device 301") according to a third embodiment.

[0121] In short, the device 301 is the device 1 of the first embodiment provided with a so-called dummy electrode 25. Specifically, for example, it is as follows.

[0122] An IDT electrode 305 of the device 301 has a pair of comb-tooth electrodes 307, similar to the IDT electrode 5 of the first embodiment. Each comb-tooth electrode 307 has a bus bar 9 and a plurality of electrode fingers 311, similar to the comb-tooth electrode 7 of the first embodiment. Each electrode finger 311 has a tip-side widened portion 311a, a tip-side main portion 311b, a narrow portion 311c, a base-side main portion 311d, a base-side widened portion 311e, and a base portion 311f, similar to the electrode finger 11 of the first embodiment.

[0123] Furthermore, unlike the first embodiment, each comb-tooth electrode 307 has a plurality of dummy electrodes 25 extending from the bus bar 9 in parallel with the plurality of electrode fingers 311. A tip of the dummy electrode 25 of one comb-tooth electrode 307 faces a tip of the electrode finger 311 of the other comb-tooth electrode 307 via a gap G1. Note that, unlike the first embodiment, a base portion 311f of the electrode finger 311 has a length (in the D2 direction) which is the sum of the length of the gap G1 (in the D2 direction) and the length of the dummy electrode 25 (in the D2 direction).

[0124] A dummy region RD is formed between the gap region RG and the busbar region RB by providing a plurality of dummy electrodes 25. The sound velocity in the dummy region RD is lower than the sound velocity in the gap region RG and higher than the sound velocity in the busbar region RB, excluding the additional film. However, the above relationship may differ depending on the additional film. For convenience, the additional film is not considered in the description of this embodiment.

[0125] The shape of the dummy electrode 25 (or, from another point of view, the sound speed in the dummy region RD) may be set appropriately. In the illustrated example, the shape of the dummy electrode 25 is a shape that protrudes in a direction perpendicular to the propagation direction of the elastic wave with a substantially constant width. In the illustrated example, the width of the dummy electrode 25 is set to be the same as the reference width of the electrode finger 311 (the width of the tip side main portion 19a, etc.). From another point of view, the sound speed in the dummy region RD is set to be equal to the sound speed in the third region R3.

[0126] Unlike the illustrated example, the width of the dummy electrode 25 may be wider or narrower than the reference width. For example, the width of the dummy electrode may be the same as the width of the tip-side widened portion 311a. In this case, the width of the base portion 311f may be the same as the width of the tip-side widened portion 311a, or may be different. From another perspective, the sound velocity of the dummy region RD may be lower or higher than the sound velocity of the third region R3. For example, the sound velocity of the dummy region RD may be equal to the sound velocity of the first region R1 or the sound velocity of the second region R2.

[0127] Also, unlike the illustrated example, the width of the dummy electrode 25 may vary depending on the position in the D2 direction. For example, the width of the dummy electrode 25 may be wider at the tip or base. From another point of view, the dummy region RD may have two or more regions with different sound velocities.

[0128] As described above, in the present embodiment, the intersection region R0 of the elastic wave device 301 includes the first region R1 to the third region R3. Therefore, the same effects as those of the first embodiment can be achieved. For example, spurious emissions can be reduced.

[0129] As shown in this embodiment, the IDT electrode 305 may have a plurality of first dummy electrodes 25A and a plurality of second dummy electrodes 25B. The plurality of first dummy electrodes 25A are connected to the same potential (same bus bar 9) as the plurality of first electrode fingers 311A, and their tips face the tips of the plurality of second electrode fingers 311B across a gap G1. The plurality of second dummy electrodes 25B are connected to the same potential (same bus bar 9) as the plurality of second electrode fingers 311B, and their tips face the tips of the plurality of first electrode fingers 311A ​​across a gap G1.

[0130] In this case, for example, three or more regions with different sound velocities are provided in the intersection region R0, and the number of regions with different sound velocities is also increased outside the intersection region R0. That is, the number of adjustment items of the velocity profile is increased. As a result, for example, it is easier to reduce spurious that cannot be reduced by only adjusting the velocity profile in the intersection region R0.

[0131] <Other Embodiments of Acoustic Wave Devices> Although not particularly shown in the drawings, the elastic wave device according to the present disclosure may be realized in various aspects other than the first to third embodiments. For example, the following aspects are as follows.

[0132] The thickness of the IDT electrode may be partially increased and / or decreased to change the mass on the upper surface 3a of the piezoelectric body 3, thereby realizing the first region R1 to the fourth region R4. For example, the change in thickness due to the additional film in the third embodiment may be the change in thickness of the IDT electrode itself.

[0133] The change in width of the electrode fingers in the first embodiment, the presence or absence of an additional film in the second embodiment, and the change in thickness of the electrode fingers can be understood as a higher-level conceptualization of the change in mass per unit length in the extension direction of the electrode fingers in the region where the electrode fingers overlap on the upper surface 3a of the piezoelectric body 3. In the following description, for convenience, the part of the electrode fingers where the mass per unit length changes relative to a reference part of the electrode fingers (for example, the main part located in the third region) may be referred to as a mass-changed part.

[0134] In the case where at least the lower surface of the additional film (see the third embodiment) is insulating, the additional film may be located not only in a position overlapping the electrode fingers but also between the electrode fingers (it may overlap the upper surface 3a of the piezoelectric body 3). For example, the additional film in the third embodiment may be expanded in the D1 direction while keeping the range in the D2 direction the same as in the third embodiment.

[0135] In the embodiment, the second region R2 is realized by providing a widening portion or an additional film (mass change portion) every other electrode finger in the arrangement of the plurality of first electrode fingers and the plurality of second electrode fingers. However, as mentioned in the explanation of the first embodiment, the second region R2 may be realized by making the width of all the electrode fingers a size between the width of the electrode fingers in the first region R1 and the width of the electrode fingers in the third region R3. The same applies to other mass change portions such as additional films.

[0136] The technique of providing a mass change portion (widened portion, etc.) every other electrode finger in the second region R2 may be applied to other regions other than the second region R2. The technique of providing a mass change portion every other electrode finger may be applied not only to cases where the mass is increased relative to a reference portion of the electrode finger (e.g., a main portion located in the third region) but also to cases where the mass is decreased. For example, in the fourth region of the first embodiment, narrow portions 11c may be provided every other electrode finger. The mass change portions may be provided every third or more electrode fingers instead of every other electrode finger in the arrangement.

[0137] The various methods for making the mass on the upper surface 3a of the piezoelectric body 3 different among the multiple regions described above may be combined as appropriate. For example, the electrode fingers may be provided with widened portions, and additional films may be provided that overlap the widened portions but not the main portions. Alternatively, for example, narrow portions may be provided without widened portions, and additional films may be provided only in the first region R1 and the second region R2 among the first region R1 to the fourth region R4.

[0138] There may be three types of regions located within the intersection region R0 and having different sound velocities. For example, the second region R2 may be omitted. Specifically, in the first embodiment, the length of the tip-side widened portion 11a may be the same as the length of the base-side widened portion 11e. Also, for example, the fourth region R4 may be omitted. In the first embodiment, the tip-side main portion 11b and the base-side main portion 11d may be connected to form one main portion without providing a narrow portion.

[0139] The first region R1 to the fourth region R4 in the embodiment are examples of the first region to the fourth region in the present disclosure. However, in an aspect in which the second region R2 is omitted, the third region R3 may be regarded as an example of the second region, and the fourth region R4 may be regarded as an example of the third region. Furthermore, in the embodiment, two adjacent regions among the first region R1 to the fourth region R4 may be regarded as an example of one region among the first region to the third region.

[0140] Conversely, there may be five or more types of regions located within the intersection region R0 and having different sound velocities. For example, a fifth region having a higher sound velocity than the second region R2 and a lower sound velocity than the third region R3 may be provided between the second region R2 and the third region R3. In this case, however, the second region R2 and the fifth region may be regarded as an example of the second region, and the fifth region and the third region R3 may be regarded as an example of the third region.

[0141] In the embodiment, three or more types of regions are provided in the intersection region R0 such that the sound speed increases toward the center in the D2 direction. However, at least one or more types of regions that do not follow the relationship that the sound speed increases toward the center in the D2 direction may be inserted between such three or more types of regions. Such regions may be used, for example, to fine-tune the characteristics of the acoustic wave device.

[0142] It should be noted that, from the present disclosure, it is possible to extract a higher-level concept that three or more regions having different sound speeds are provided in the intersection region R0. In this higher-level concept, it is not essential that three or more regions are provided so that the sound speed becomes higher toward the center in the D2 direction.

[0143] <Examples of using elastic wave devices> The acoustic wave device may be used in various aspects such as a resonator and a filter. Examples of uses of the acoustic wave device are described below. Specifically, the following description will be given in the following order. An example of a resonator An example of a splitter An example of a communication device

[0144] A resonator, a branching filter, and a communication device are all examples of applications of an elastic wave device. In the explanation of the branching filter, an example of a filter as an example of an application of an elastic wave device will also be explained. In the following explanation, the elastic wave device 1 of the first embodiment will be taken as an example of an elastic wave device. However, it goes without saying that other elastic wave devices may also be used.

[0145] (An example of a resonator) FIG. 7 is a plan view showing the configuration of the resonator 31. As shown in FIG.

[0146] The resonator 31 is configured as a so-called one-port acoustic wave resonator. When an electrical signal of a predetermined frequency is input to one of two terminals 33 conceptually and diagrammatically shown in FIG. 7, the resonator 31 resonates and can output the resonated signal from the other of the two terminals 33.

[0147] The resonator 31 has, for example, a piezoelectric body 3 (see FIG. 2 and the like), as well as an IDT electrode 5 and a pair of reflectors 35 located on an upper surface 3a of the piezoelectric body 3. The resonator 31 may be considered to include the elastic wave device 1 according to the first embodiment, or may be considered to be included in the device 1. As described above, the resonator 31 includes the piezoelectric body 3 (and other layers that affect elastic waves). However, for convenience, the combination of the IDT electrode 5 and the pair of reflectors 35 may be expressed as the resonator 31.

[0148] The pair of reflectors 35 are formed, for example, by the same conductor layer as the conductor layer forming the IDT electrode 5. In a mode in which an additional film overlapping all or part of the IDT electrode 5 is provided, an additional film overlapping all or part of the reflector 35 may be provided. The pair of reflectors 35 are located on both sides of the IDT electrode 5 in the propagation direction of the acoustic wave. Each reflector 35 may be, for example, in an electrically floating state, or may be given a reference potential.

[0149] Each reflector 35 is formed, for example, in a lattice shape. That is, the reflector 35 includes a pair of bus bars 37 facing each other and a plurality of strip electrodes 39 extending between the pair of bus bars 37. Note that, like the plurality of electrode fingers 11, the plurality of strip electrodes 39 may actually be provided in greater number than the number shown in the figure.

[0150] Busbar 37 has, for example, a configuration generally similar to that of busbar 9 of IDT electrode 5, and the description of busbar 9 may be applied to busbar 37. Busbar 37 is, for example, arranged in series with busbar 9 in the propagation direction of the elastic wave. In addition, the width of busbar 37 is set to be equal to the width of busbar 9.

[0151] Unlike the illustrated example, the width of busbar 37 may be different from the width of busbar 9. Busbar 37 may be positioned in a different position in the D2 direction from busbar 9. When busbar 9 is inclined in the propagation direction of the elastic wave, busbar 37 may be inclined in the same manner as busbar 9, or may be parallel to the propagation direction of the elastic wave.

[0152] The schematic configuration of the multiple strip electrodes 39 is similar to that of the electrode fingers 11 of the IDT electrode 5, except that the multiple strip electrodes 39 are bridged across a pair of bus bars 37. The description of the electrode fingers 11 may be applied to the strip electrode 39 as appropriate. The multiple strip electrodes 39 are arranged in the propagation direction of the acoustic wave so as to follow the arrangement of the multiple electrode fingers 11. The pitch of the multiple strip electrodes 39 and the pitch between the electrode fingers 11 adjacent to the reflector 35 and the strip electrode 39 adjacent to the IDT electrode 5 are, for example, equal to the pitch of the multiple electrode fingers 11.

[0153] The specific planar shape of the strip electrode 39 (from another point of view, the change in width (length in the D1 direction) according to the position in the D2 direction) is arbitrary. In the illustrated example, the strip electrode 39 has a shape having a widened portion 39b in a region obtained by extending the first region R1 (see FIG. 1, etc.) in the D1 direction. The width of the portion other than the widened portion 39b is, for example, equal to the reference width of the electrode finger 11 (width of the tip side main portion 11b, etc.). The width of the widened portion 39b is, for example, equal to the width of the tip side widened portion 11a and the base side widened portion 11e of the electrode finger 11. Although no particular reference numerals or symbols are given to the planar shape of the strip electrode 39 as described above, in the region obtained by extending the intersection region R0 (see FIG. 1, etc.) to the reflector 35, two (three) types of regions having different sound velocities are formed.

[0154] Unlike the illustrated example, the region in which the intersection region R0 is extended to the reflector 35 may have three or more regions with different sound velocities. For example, the strip electrodes 39 may be configured such that two types of widened portions having different lengths in the D2 direction are alternately arranged, similar to the electrode fingers 11. The strip electrodes 39 may have a narrowed portion on the center side in the D2 direction, similar to the electrode fingers 11. Two types of widened portions and narrowed portions may be combined. Conversely to the above, the region in which the intersection region R0 is extended to the reflector 35 may have a constant sound velocity. That is, the strip electrode 39 may have a constant width over its length. As can be understood from the illustrated example, the number and type of regions related to the sound velocity in the IDT electrode 5 may be different from the number and type of regions related to the sound velocity in the reflector 35 (illustrated example) or may be the same.

[0155] In the reflector 35, as in the IDT electrode 5, the method for changing the mass on the upper surface 3a of the piezoelectric body 3 is not limited to changing the width of the strip electrode 39, and various other methods may be used. In one resonator 31, the method for changing the mass may be the same for the IDT electrode 5 and the reflector 35 (in the illustrated example) or may be different.

[0156] (An example of a splitter) 8 is a circuit diagram showing a schematic configuration of a branching filter 101 (e.g., a duplexer). As can be seen from the reference numerals in the upper left corner of the figure, in this figure, the comb-tooth electrode 7 is shown in a schematic form with a two-pronged fork shape, and the reflector 35 is represented by a single line bent at both ends.

[0157] The splitter 101 has, for example, a transmit filter 109 that filters a transmit signal from the transmit terminal 105 and outputs the signal to the antenna terminal 103, and a receive filter 111 that filters a receive signal from the antenna terminal 103 and outputs the signal to a pair of receive terminals 107.

[0158] The transmit filter 109 is configured, for example, as a ladder filter configured by connecting a plurality of resonators 31 (series resonators 31S and parallel resonators 31P) in a ladder configuration. That is, the transmit filter 109 has a plurality of series resonators 31S (or one) connected in series between the transmit terminal 105 and the antenna terminal 103, and a plurality of parallel resonators 31P (or one) connecting the series line (series arm) and a reference potential section (reference symbol omitted).

[0159] The receiving filter 111 is configured to include, for example, a resonator 31 and a multimode filter (including a double-mode filter) 113. The multimode filter includes a double-mode filter. The multimode filter 113 has a plurality of IDT electrodes 5 (three in the illustrated example) arranged in the propagation direction of the acoustic wave, and a pair of reflectors 35 arranged on both sides thereof.

[0160] At least one of the multiple resonators of the transmit filter 109 (ladder filter) may include the acoustic wave device 1 (IDT electrode 5) according to the embodiment. In terms of one IDT electrode 5 included in the device 1, the transmit filter 109 includes the device 1 and one or more other IDT electrodes that are located on the upper surface 3a of the piezoelectric body 3 of the device 1 and are connected in a ladder configuration with the one IDT electrode 5 to form a ladder filter (in the illustrated example, the other IDT electrodes are also the IDT electrode 5 according to the first embodiment).

[0161] At least one of the multiple IDT electrodes of the multimode filter 113 may include the acoustic wave device 1 (IDT electrode 5) according to the embodiment. In terms of one IDT electrode 5 included in the device 1, the multimode filter 113 includes the device 1 and one or more other IDT electrodes (in the illustrated example, the other IDT electrodes are also the IDT electrode 5 according to the first embodiment) that are located on the upper surface 3a of the piezoelectric body 3 of the device 1 and are arranged in the acoustic wave propagation direction with respect to the one IDT electrode 5 to form a multimode filter.

[0162] In addition, each of the splitter 101, the transmit filter 109 (ladder type filter), the receive filter 111 and the multi-mode filter 113 may be considered to include the device 1 of the first embodiment, or may be considered to be included in the device 1.

[0163] The multiple IDT electrodes 5 (and reflectors 35) of the branching filter 101 may be provided on one piezoelectric body 3 (substrate) or may be distributed across two or more piezoelectric bodies 3. For example, the multiple resonators 31 constituting the transmit filter 109 may be provided on the same piezoelectric body 3. Similarly, the resonators 31 and the multi-mode filter 113 constituting the receive filter 111 may be provided on the same piezoelectric body 3. The transmit filter 109 and the receive filter 111 may be provided on the same piezoelectric body 3 or on different piezoelectric bodies 3. In addition to the above, for example, multiple series resonators 31S may be provided on the same piezoelectric body 3, and multiple parallel resonators 31P may be provided on another same piezoelectric body 3.

[0164] 8 is merely one example of the configuration of the duplexer 101. Therefore, for example, the receiving filter 111 may be configured with a ladder filter like the transmitting filter 109. Also, the transmitting filter 109 may have a multimode filter 113. The duplexer 101 is not limited to a duplexer, and may be, for example, a diplexer or a multiplexer including three or more filters.

[0165] (Communication Equipment) 9 is a block diagram showing a main part of a communication device 151 as an example of a use of the elastic wave device 1. The communication device 151 performs wireless communication using radio waves, and includes a duplexer 101.

[0166] In the communication device 151, a transmission information signal TIS including information to be transmitted is modulated and frequency-raised (converted into a high-frequency signal having a carrier frequency) by an RF-IC (Radio Frequency Integrated Circuit) 153 to become a transmission signal TS. Unnecessary components outside the transmission passband are removed from the transmission signal TS by a bandpass filter 155, amplified by an amplifier 157, and input to a splitter 101 (transmission terminal 105). Then, the splitter 101 (transmission filter 109) removes unnecessary components outside the transmission passband from the input transmission signal TS, and outputs the transmission signal TS after removal from an antenna terminal 103 to an antenna 159. The antenna 159 converts the input electrical signal (transmission signal TS) into a wireless signal (radio wave) and transmits it.

[0167] Furthermore, in the communication device 151, a radio signal (radio wave) received by the antenna 159 is converted by the antenna 159 into an electric signal (received signal RS) and input to the duplexer 101 (antenna terminal 103). The duplexer 101 (receiving filter 111) removes unnecessary components outside the receiving passband from the inputted received signal RS and outputs it from the receiving terminal 107 to the amplifier 161. The outputted received signal RS is amplified by the amplifier 161, and the unnecessary components outside the receiving passband are removed by the bandpass filter 163. Then, the received signal RS is frequency-downgraded and demodulated by the RF-IC 153 to become a received information signal RIS.

[0168] The transmission information signal TIS and the reception information signal RIS may be low-frequency signals (baseband signals) containing appropriate information, for example, analog audio signals or digitized audio signals. The passband of the wireless signal may be set appropriately and may conform to various known standards. The modulation method may be any of phase modulation, amplitude modulation, frequency modulation, or a combination of two or more of these. Although the direct conversion method is exemplified as the circuit method, other appropriate methods may be used, for example, double superheterodyne method. Also, FIG. 9 shows only the main parts in a schematic manner, and low-pass filters, isolators, etc. may be added at appropriate positions, and the positions of amplifiers, etc. may be changed.

[0169] The acoustic wave device 1 may be used in various aspects other than the above-described aspects. For example, the acoustic wave device 1 may be used as a two-port resonator or a transversal filter.

[0170] <Example> The effects of the elastic wave device 1 according to the embodiment were confirmed by measuring the characteristics of a prototype of the resonator 31 (FIG. 7) according to the embodiment and calculating the characteristics of the resonator 31 by simulation. Some examples are given below.

[0171] (First Comparative Example and First Example) FIG. 10 is a diagram showing the characteristics of the resonators according to the first comparative example and the first embodiment.

[0172] In Fig. 10, the horizontal axis represents frequency. The vertical axis represents the phase of impedance. Line LC1 represents the characteristics of the first comparative example. Line LE1 represents the characteristics of the first embodiment. Fig. 10 was obtained by measuring the characteristics of a prototype.

[0173] The resonator 31 has a resonant frequency at which the absolute value of the impedance is a minimum value, and an anti-resonant frequency at which the absolute value of the impedance is a maximum value. In general, in the range between the resonant frequency and the anti-resonant frequency, the closer the phase of the impedance is to 90°, the better the characteristics of the resonator 31. Outside the above range, the closer the phase of the impedance is to -90°, the better the characteristics of the resonator 31. In FIG. 10, the range of the horizontal axis roughly corresponds to the range between the resonant frequency and the anti-resonant frequency.

[0174] The first example is similar to the resonator 31 according to the first embodiment. In the first comparative example, unlike the first example, the electrode fingers 11 of the IDT electrode 5 and the strip electrode 39 of the reflector 35 have a constant width (reference width) over their entire length. Also, unlike the first example, the first comparative example has a dummy electrode. Other conditions are generally similar between the first comparative example and the first example.

[0175] 10, in the first embodiment, the number and magnitude of spurious signals are reduced compared to the first comparative example. That is, it was confirmed by actual measurements that the spurious signals are reduced by forming the first region R1 to the fourth region R4 within the intersection region R0.

[0176] The conditions common to the first comparative example and the first embodiment are shown below. Piezoelectric: Material:LT Cut angle: 50° rotation Y cut X propagation Thickness: 0.65μm ·Low sound velocity layer (middle layer 17): Material: SiO2 Thickness: 0.22μm ·High sonic layer (support substrate 15): Material:Si Thickness: Sufficient thickness for pitch p (200 μm) ·IDT electrode: Material: Ti and Al laminated structure Thickness: Ti: 60 Å Al: 1400Å Electrode finger: Number of pieces: 250 Pitch: 1.03μm Width of intersection area R0: 40p ·Reflector: Material and thickness: same as IDT electrode Strip Electrode: Number of pieces: 30 (1 reflector) Pitch: Same as the electrode finger pitch

[0177] Other conditions in the first embodiment are as follows: ·First area R1 Electrode finger duty: 0.65 Width of one first region R1 (D2 direction): 2.0 μm ·Second area R2 Electrode finger duty: Repeated between 0.65 and 0.50 Width of one second region R2 (D2 direction): 0.5 μm ·Third area R3 Electrode finger duty: 0.50 Width of one third region R3 (D2 direction): 17.71 μm ·4th area R4 Electrode finger duty: 0.40 Width of the fourth region R4 (D2 direction): 0.78 μm Gap region RG Electrode finger duty: 0.50 Width of one gap region RG (D2 direction): 0.38 μm The configuration of the reflector 35 of the first embodiment is similar to the configuration shown in Fig. 7. For parameters of the strip electrode 39 of the first embodiment, please refer to the parameters of the first region R1 and the third region R3 described above.

[0178] Other conditions of the first comparative example are as follows. Duty of electrode fingers: same as the duty of the third region R3 in the first embodiment Dummy electrode: Length (D2 direction): 3.7 μm Duty: Same as electrode finger duty Width of one gap region RG (D2 direction): 0.30 μm Strip electrode duty: same as electrode finger duty

[0179] (Second Comparative Example and First Example) FIG. 11 is a diagram showing the characteristics of the resonators according to the second comparative example and the first embodiment (already described), and is similar to FIG.

[0180] Fig. 11 was obtained by measuring the characteristics of a prototype, similar to Fig. 10. In Fig. 11, line LC2 shows the characteristics of the second comparative example. Line LE1 shows the characteristics of the first embodiment, and is the same as line LE1 shown in Fig. 10.

[0181] In the electrode finger of the second comparative example, unlike the electrode finger 11 of the first embodiment, the tip side widened portion and the base side widened portion have the same length in the D2 direction. Moreover, in the second comparative example, the electrode finger has no narrow portion. That is, in the second comparative example, like an IDT electrode using a general piston mode, the intersection region has only two (three) types of regions with different sound speeds. Moreover, like the strip electrode of the reflector of the first comparative example, the strip electrode of the reflector of the second comparative example has a constant width (reference width) over its entire length. Other conditions are generally similar between the first comparative example and the first embodiment.

[0182] 11, in the first embodiment, the number and magnitude of spurious signals are reduced compared to the first comparative example. That is, it was confirmed by actual measurements that the spurious signals are reduced by forming the first region R1 to the fourth region R4 within the intersection region R0.

[0183] The above-mentioned conditions common to the first comparative example and the first embodiment are also common to the second comparative example and the first embodiment. The width (D2 direction) of the gap region in the second comparative example is the same as the width of the gap region in the first embodiment. Other conditions in the second comparative example are as follows. Low sound speed region (corresponding to the first region R1) Electrode finger duty: 0.65 Width of one low sound velocity region (D2 direction): 1.5 μm · Main region (region between the two low sound speed regions) Electrode finger duty: 0.50 Width (D2 direction): 38.2μm

[0184] (Second Example) FIG. 12 is a diagram showing the characteristics of the resonators according to the first and second comparative examples (both already described) and the second embodiment, and is a diagram similar to FIG.

[0185] Unlike Fig. 10 and Fig. 11, Fig. 12 was obtained by simulation calculation. In Fig. 12, lines LC1 and LC2 show the characteristics of the first and second comparative examples. Line LE2 shows the characteristics of the second embodiment. For convenience, the lines showing the characteristics of the first and second comparative examples are given the same reference characters (LC1 and LC2) as Fig. 10 and Fig. 11.

[0186] The second embodiment is different from the first embodiment in that the narrow portion 11c is not provided. That is, in the second embodiment, the intersection region does not have the fourth region R4, but has three (five) regions (corresponding to the first region R1 to the third region R3) with different sound speeds. The rest of the configuration of the second embodiment is the same as that of the first embodiment.

[0187] 12, in the second embodiment, the magnitude of the spurious is reduced compared to the first and second comparative examples. That is, it was confirmed by simulation calculation that the spurious is reduced not only by forming regions corresponding to the first region R1 and the third region R3 in the intersection region R0 but also by forming the second region R2 (or, from another point of view, without forming the fourth region R4).

[0188] (Third Example) FIG. 13 is a diagram showing the characteristics of the resonators according to the first and second comparative examples (both already described) and the third embodiment, and is a diagram similar to FIG.

[0189] Fig. 13, like Fig. 12, was obtained by simulation calculation. In Fig. 13, lines LC1 and LC2 show the characteristics of the first and second comparative examples, and are the same as lines LC1 and LC2 in Fig. 12. Line LE3 shows the characteristics of the third embodiment.

[0190] In the third embodiment, the length (D2 direction) of the base side widened portion 11e is the same as the length of the tip side widened portion 11a in the first embodiment. That is, in the second embodiment, the intersection region does not have the second region R2, and has three (five) regions (corresponding to the first region R1, the third region R3, and the fourth region) with different sound speeds. The other configurations of the third embodiment are the same as those of the first embodiment.

[0191] 13, in the third embodiment, the magnitude of the spurious is reduced compared to the first and second comparative examples. That is, it was confirmed by simulation calculation that the spurious can be reduced not only by forming regions corresponding to the first region R1 and the third region R3 in the intersection region R0 but also by forming the fourth region R4 (or, from another point of view, without forming the second region R2).

[0192] (Fourth to Seventh Examples) FIG. 14 is a diagram showing the characteristics of the resonators according to the fourth to seventh embodiments, and is similar to FIG.

[0193] Fig. 14 is obtained by simulation calculation, similar to Fig. 12. In Fig. 14, lines LE4, LE5, LE6 and LE7 show the characteristics of the fourth, fifth, sixth and seventh embodiments.

[0194] In the fourth to seventh examples, the width (length in the D2 direction) of the fourth region R4 is made different from that of the first example. Specifically, the width of the fourth region R4 is as follows. Fourth Example: 0.5p Fifth Example: 1.0p Sixth Example: 1.5p Seventh Example: 2.0p

[0195] In the above-mentioned range of the width of the fourth region R4, the smaller the width, the smaller the spurious response. In FIG. 14, since the lines LE4 to LE7 overlap each other and comparison is difficult, the phase (°) of the impedance in each example for the spurious responses S1 to S4 in the figure is shown below. The larger the value shown below, the smaller the spurious response. 0.5p 1.0p 1.5p 2.0p S1: 52 38 22 19 S2: 65 52 39 33 S3: 77 78 86 87 S4: 76 73 69 67 [Explanation of symbols]

[0196] 1...acoustic wave device, 3...piezoelectric body, 3a...upper surface (first surface), 5...IDT electrode, 11A...first electrode finger, 11B...second electrode finger, R0...intersection region, R1...first region, R2...second region, R3...third region.

Claims

1. a piezoelectric body having a first surface; an IDT electrode located on the first surface; Equipped with The IDT electrode is A plurality of first electrode fingers; a plurality of second electrode fingers connected to a potential different from that of the plurality of first electrode fingers and arranged alternately with the plurality of first electrode fingers in a direction of propagation of an acoustic wave; An intersection region in which the first electrode fingers and the second electrode fingers overlap in the acoustic wave propagation direction is a first region located on a tip side of the first electrode fingers or the second electrode fingers in a first direction in which the first electrode fingers and the second electrode fingers extend, the first region having a first sound velocity; A third region having a width in the first direction, located toward the center in the first direction from the first region, and having a third sound speed higher than the first sound speed; A fourth region having a width in the first direction, located closer to the center in the first direction than the third region, and having a fourth sound speed higher than the third sound speed. Elastic wave device.

2. The length of the fourth region in the first direction is less than 1.5 times the pitch of the first electrode fingers and the second electrode fingers. The acoustic wave device according to claim 1 .

3. The third region is located on both sides of the fourth region, and a total width of the third regions is 50% or more of a width of the intersection region. The acoustic wave device according to claim 1 .

4. the first region is located on both sides of the third region, The sum of the widths of the first regions is greater than the width of the fourth region. The acoustic wave device according to claim 1 .

5. The fourth region is located at the center of the intersection region in the first direction. The acoustic wave device according to claim 1 .

6. a plurality of first dummy electrodes connected to the same potential as the plurality of first electrode fingers and having tips facing tips of the plurality of second electrode fingers with gaps therebetween; a plurality of second dummy electrodes connected to the same potential as the plurality of second electrode fingers and having tips facing tips of the plurality of first electrode fingers with gaps therebetween; The acoustic wave device according to claim 1 , further comprising:

7. The elastic wave device according to claim 1 , one or more other IDT electrodes located on the first surface and connected to the IDT electrodes in a ladder configuration to form a ladder filter; The filter has the following characteristics:

8. The elastic wave device according to claim 1 , one or more other IDT electrodes located on the first surface and arranged in the acoustic wave propagation direction relative to the IDT electrodes to configure a multimode filter; The filter has the following characteristics:

9. An antenna terminal; a transmission filter connected to the antenna terminal; a receiving filter connected to the antenna terminal; It has At least one of the transmission filter and the reception filter is constructed by the filter according to claim 7 or 8. Duplexer.

10. The duplexer according to claim 9 , an antenna connected to the antenna terminal; an IC connected to the transmit filter and the receive filter; A communication device having the above configuration.

Images