Elastic wave apparatus, filters, demultiplexers and communication devices

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 conversion from an acoustic wave to an electrical signal and conversion from an electrical signal to an acoustic wave, a filter including the acoustic wave device, a demultiplexer including the filter, and a communication device including the demultiplexer.

Background Art

[0002] As an acoustic wave device, one having a piezoelectric layer and an IDT (Interdigital Transducer) electrode located on the piezoelectric layer is known (for example, Patent Document 1 below). The IDT electrode has a pair of comb teeth 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 teeth electrodes are arranged to mesh with each other. A region where the plurality of electrode fingers of one comb tooth electrode overlap the plurality of electrode fingers of the other comb tooth electrode in the propagation direction of the acoustic wave is called an intersection region or the like, 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 in the direction in which the plurality of electrode fingers extend and a high sound velocity region on the central side in the extending direction. The sound velocity in the low sound velocity region is lower than the sound velocity in the high sound velocity region. With such a configuration, a so-called piston mode is utilized, and thus spurious of the transverse mode is reduced.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] An elastic wave apparatus according to one aspect of the present disclosure comprises a piezoelectric body having a first surface and an IDT electrode located on the first surface. The IDT electrode has a plurality of first electrode fingers and a plurality of second electrode fingers connected to a different potential from the plurality of first electrode fingers and arranged alternately with the plurality of first electrode fingers in the elastic wave propagation direction. The intersection region in which the plurality of first electrode fingers and the plurality of second electrode fingers overlap in the elastic wave propagation direction has 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 further towards the center than the first region in the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers extend, and has a higher velocity of sound than the first region. The third region is located further towards the center than the second region, and has a higher velocity of sound than the second region.

[0006] A filter according to one aspect of the present disclosure comprises the acoustic wave apparatus described above, and one or more other IDT electrodes located on the first surface and connected in a ladder-like manner to the IDT electrode to constitute a ladder-type filter.

[0007] A filter according to one aspect of the present disclosure comprises the above-mentioned elastic wave apparatus and one or more other IDT electrodes located on the first surface and arranged in the direction of elastic wave propagation relative to the IDT electrode to constitute a multimode filter.

[0008] A demultiplexer according to one aspect of the present disclosure includes an antenna terminal, a transmit filter connected to the antenna terminal, and a receive filter connected to the antenna terminal, wherein at least one of the transmit filter and the receive filter is composed of one of the filters described above.

[0009] A communication device according to one aspect of this disclosure includes the above-mentioned demultiplexer, an antenna connected to the antenna terminal, and an IC (Integrated Circuit) connected to the transmit filter and the receive filter. [Brief explanation of the drawing]

[0010] [Figure 1] This is a plan view showing the configuration of the elastic wave apparatus according to the first embodiment. [Figure 2] This figure shows an example of a cross-section along line II-II in Figure 1. [Figure 3] This figure shows another example of a cross-section along line II-II in Figure 1. [Figure 4] This is a plan view showing the configuration of the elastic wave apparatus according to the second embodiment. [Figure 5] Figure 4 is a cross-sectional view along the VV line. [Figure 6] This is a plan view showing the configuration of the elastic wave apparatus according to the third embodiment. [Figure 7] This is a plan view showing the configuration of an elastic wave resonator according to the embodiment. [Figure 8] This is a schematic circuit diagram showing the configuration of a demultiplexer according to the embodiment. [Figure 9] This is a block diagram showing the configuration of a communication device according to the embodiment. [Figure 10] This figure shows the characteristics of the resonator according to the first comparative example and the first embodiment. [Figure 11] This figure shows the characteristics of the resonator according to the second comparative example and the first embodiment. [Figure 12] This figure shows the characteristics of the resonator according to the first and second comparative examples and the second embodiment. [Figure 13] This figure shows the characteristics of the resonators according to the first and second comparative examples and the third embodiment. [Figure 14] This figure shows the characteristics of the resonators according to the 4th to 7th embodiments. [Modes for carrying out the invention]

[0011] The embodiments relating to this disclosure will be described below with reference to the drawings. The figures used in the following description are schematic. Therefore, for example, the dimensional ratios, etc., on the drawings do not necessarily correspond to those of reality. Dimensional ratios, etc., may not match between drawings. Certain shapes or dimensions, etc., may be shown in an exaggerated manner.

[0012] The elastic wave device according to the present disclosure may have any direction defined as upward or downward. However, hereinafter, for convenience, a rectangular coordinate system composed of D1 axis, D2 axis and D3 axis is defined, and the positive side of the D3 axis is defined as upward, and terms such as upper surface or lower surface may be used. Also, when referring to a plan view or a plane perspective view, unless otherwise specified, it means looking in the D3 direction. The D1 axis is defined to be parallel to the propagation direction of the elastic wave propagating along the upper surface of the piezoelectric body described later, the D2 axis is defined to be parallel to the upper surface of the piezoelectric body and orthogonal to the D1 axis, and the D3 axis is defined to be orthogonal to the upper surface of the piezoelectric body.

[0013] For the embodiments described after the description of the first embodiment, basically, only the differences from the previously described embodiments will be described. For matters not specifically mentioned, they may be the same as those in the previously described embodiments or inferred from the previously described embodiments.

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

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

[0016] When a voltage is applied to the IDT electrode 5, an elastic wave that propagates in the D1 direction in the intersection region R0 of the piezoelectric body 3 is excited. And / or, when the elastic wave propagates in the D1 direction in the intersection region R0, charges are generated in the piezoelectric body 3 and a voltage is applied to the IDT electrode 5. The device 1 may constitute, for example, a resonator and / or a filter that utilizes such conversion between an elastic wave and a voltage (electrical signal). In the following, the D1 direction may sometimes 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 sound velocity profile 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 the corresponding positions of both are connected by a dotted line. The axis parallel to the D1 direction indicates the sound velocity V. On this axis, the right side (+D1 side) of FIG. 1 corresponds to the side with a higher sound velocity.

[0018] Note that the graph on the right side of FIG. 1 only shows the ranking of the sound velocities in a plurality of regions. That is, the actual values are not reflected in the absolute value of the sound velocity in each region, the difference in the sound velocity between the plurality of regions, and the ratio of the sound velocities between the plurality of regions. Also, in FIG. 1, since a part of the shape of the IDT electrode 5 is exaggerated, as will be described in detail later, there is a contradiction between the dimensional ratio of the IDT electrode 5 and the velocity profile.

[0019] In a general elastic wave device, the sound velocity in the intersection region R0 is constant throughout. Also, in an elastic wave device that utilizes the so-called piston mode, the intersection region R0 has a high sound velocity region on the central side in the D2 direction and low sound velocity regions located on both sides in the D2 direction with respect to the high sound velocity region. That is, two types of 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 types of regions with different sound velocities are formed in the intersection region R0. In the illustrated example, four types of regions, namely the first region R1 to the fourth region R4, are formed. Thereby, for example, spurious of the transverse mode can be reduced.

[0021] In the first embodiment, regions with different sound velocities are achieved by making the planar shape of the IDT electrode 5 novel. In other words, other configurations may be of various types, for example, known types. The description of the first embodiment will generally proceed in the following order. (1) Overview of IDT electrodes (Figure 1) (2) Overview of the speed profile (Figure 1) (3) Details of the planar shape of the IDT electrode (Figure 1) (4) Example of dimensions of each part of the electrode finger (described later) of the IDT electrode (Figure 1) (5) Various configurations of substrates containing piezoelectric materials (Figures 2 and 3) (6) Other components of the elastic wave apparatus (7) Summary of the first embodiment

[0022] In the explanation in (1) above, the IDT electrode 5 will be described using the embodiment shown in Figure 1 as an example, with respect to matters that may be considered known embodiments. However, this explanation may include descriptions of novel embodiments without prior notice. In the explanation in (3) above, the planar shape of the IDT electrode 5 related to the velocity profile will be described.

[0023] (Overview of IDT electrodes) The IDT electrode 5 is composed of a conductive layer that overlaps 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 busbar 9 and a plurality of electrode fingers 11 extending in parallel from the busbar 9. In the following description, the electrode finger 11 of one comb-tooth electrode 7 (the electrode finger 11 extending from the -D2 busbar 9 to the +D2 side in Figure 1) may be referred to as the first electrode finger 11A. The electrode finger 11 of the other comb-tooth electrode 7 (the electrode finger 11 extending from the +D2 busbar 9 to the -D2 side in Figure 1) may be referred to as the second electrode finger 11B.

[0024] A pair of comb-tooth electrodes 7 are arranged so that multiple electrode fingers 11 interlock (cross each other). That is, multiple first electrode fingers 11A and multiple second electrode fingers 11B are arranged alternately, with each other interlocking. In this case, the multiple first electrode fingers 11A and multiple second electrode fingers 11B may be arranged alternately one by one (as shown in the illustration), or they may be arranged alternately in groups of two or more. Furthermore, there may be specific parts due to thinning or the like. In describing the embodiment, the configuration in which they are arranged alternately one by one will be used as an example.

[0025] The busbars 9 are formed, for example, in a long, linear shape extending in the direction of elastic wave propagation (direction D1) with a generally constant width. A pair of busbars 9 face each other in a direction perpendicular to the direction of elastic wave propagation (direction D2). The busbars 9 may have varying widths or be inclined with respect to the direction of elastic wave propagation.

[0026] The multiple electrode fingers 11, for example, have the same shape and dimensions as each other. Each electrode finger 11 is formed in an elongated shape, for example, with its centerline extending linearly in a direction perpendicular to the direction of elastic wave propagation (D2 direction).

[0027] Multiple electrode fingers 11 are arranged in the propagation direction. When we say they are arranged in the propagation direction, the 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 shown in the example), or it 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 multiple electrode fingers 11 (for example, the distance between the centers of two adjacent electrode fingers 11) is basically constant within the IDT electrode 5. However, the IDT electrode 5 may have some parts that are unique in terms of pitch p. Examples of unique parts include a narrow-pitch section where the pitch p is narrower than the majority (for example, 80% or more), a wide-pitch section where the pitch p is wider than the majority, and a decimated section where a small number of electrode fingers 11 are substantially removed.

[0029] In the following, when referring to pitch p, unless otherwise specified, it means the pitch of the portion excluding the special part described above (the majority of the multiple electrode fingers 11). Furthermore, if the pitch changes even in the majority of the multiple electrode fingers 11 excluding the special part, the average value of the pitches of the majority of the multiple electrode fingers 11 may be used as the value of pitch p.

[0030] The number of electrode fingers 11 may be set appropriately according to the required electrical characteristics of the IDT electrode 5 (device 1). Since Figure 1 is a schematic diagram, the number of electrode fingers 11 is shown to be small. In reality, more electrode fingers 11 may be arranged than shown. For example, the number of electrode fingers 11 may be 100 or more. Note that Figure 1 may be considered as a diagram showing only a part of the IDT electrode 5.

[0031] The tip of each electrode finger 11 faces the edge of the busbar 9 to which it is not connected, via a gap G1. The lengths of the multiple gaps G1 in the D2 direction are, for example, identical to one another.

[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 multiple electrode fingers 11, causing 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) to vibrate. This excites elastic waves propagating along the upper surface 3a. At this time, when the multiple elastic waves excited by the multiple electrode fingers 11 have half wavelengths approximately equal to the pitch p, they become in phase with each other in the direction perpendicular to the multiple electrode fingers 11 (D1 direction), and their amplitudes are added together. In other words, elastic waves propagating in the D1 direction with a pitch p as half wavelength are the most easily excited. As a result, of the voltage applied to the IDT electrode 5, mainly the component having a frequency equivalent to that of an elastic wave with a pitch p as half wavelength is converted into an elastic wave. Furthermore, when an elastic wave is generated in the region where one pair of comb-tooth electrodes 7 are arranged on the upper surface 3a, the elastic wave, which propagates mainly in the direction D1 with a pitch p of approximately half a wavelength, is converted into a voltage by the opposite principle to the above. A resonator or filter can be realized using this principle.

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

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

[0035] The pitch p of the electrode finger 11 is, as described above, 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 between 0.5 μm and 15 μm. The length of the electrode finger 11 may be, for example, 10 p or more, or 20 p or more, and may also be 100 p or less, or 50 p 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 its position in the planar direction (the direction parallel to the D1-D2 plane). The thickness of the conductor layer may be set appropriately according to the characteristics required of the apparatus 1. For example, the thickness of the conductor layer may be 0.04p or more and 0.20p or less, and / or 50nm or more and 600nm or less.

[0037] The conductive layer is formed of, for example, a metal. The metal may be of any suitable type, for example, aluminum (Al) or an alloy mainly composed of Al (Al alloy). An Al alloy is, for example, an Al-copper (Cu) alloy. The conductive layer may be composed of multiple metal layers. For example, the conductive 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, for example, to strengthening the bonding between Al or the Al alloy and the piezoelectric body 3.

[0038] (Overview of speed profile) In a plan view of the upper surface 3a of the piezoelectric element 3, the region where the IDT electrode 5 is located can be divided into the following three regions in the D2 direction based on the configuration of the IDT electrode 5: the intersection region R0 where multiple first electrode fingers 11A and multiple second electrode fingers 11B overlap in the direction of elastic wave propagation; the gap region RG where the gap G1 is located; and the busbar region RB where the busbar 9 is located.

[0039] The intersection region R0 may be considered as the 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 assuming a line connecting predetermined parts (e.g., tips) of multiple electrode fingers 11, if the position of the above line differs depending on which position within the width of the electrode fingers 11 is used as the reference point, the center line of the electrode fingers 11 may be used as the reference point.

[0040] In the illustrated example, the lines connecting the tips of the multiple first electrode fingers 11A and the lines connecting the tips of the multiple second electrode fingers 11B are parallel straight lines. In other words, the intersection region R0 is a rectangle. More specifically, the lines connecting the tips are perpendicular to the electrode fingers 11, and therefore the intersection region R0 is a rectangle with sides parallel to the D1 direction. This rectangle is, for example, a rectangle that is longer in the D1 direction, unlike in Figure 1. Note that the intersection region R0 may have a shape other than a rectangle. For example, the intersection region R0 may be a parallelogram shape in which the lines connecting the tips are inclined in the D1 direction.

[0041] It should be noted that the descriptions of various regions (R0, R1-R4, RG, and RB) in this embodiment may only apply to a portion of the IDT electrode in the D1 direction. For example, in the illustrated example, the line connecting the tips of the multiple first electrode fingers 11A is straight across all of the first electrode fingers 11A. However, the line connecting the tips of the multiple first electrode fingers 11A may be straight only for a predetermined number (e.g., 10 or more). In other words, the effects achieved in this embodiment may be obtained in only a portion 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] The gap region RG may be considered as the region sandwiched between the line connecting the tips of the multiple first electrode fingers 11A (or multiple second electrode fingers 11B) and the edge of the busbar 9 facing the tips of the multiple first electrode fingers 11A. In the illustrated example, the gap region RG is rectangular in shape with a long side parallel to the D1 direction. However, the gap region RG may have a shape other than a rectangle. For example, if the intersection region R0 is parallelogram-shaped as described above, the gap region RG may be parallelogram-shaped with four sides parallel to each of the four sides of the intersection region R0.

[0043] The busbar region RB may be considered as the region sandwiched between the edge of the busbar 9 on the electrode finger 11 side and the edge on the opposite side. In the illustrated example, the busbar region RB is rectangular with a long side parallel to the D1 direction. However, the busbar region RB may have a shape other than a rectangle. For example, if the intersection region R0 and the gap region RG are parallelograms as described above, the busbar region RB may be a parallelogram with four sides parallel to each of the four sides of the intersection region R0. Alternatively, the busbar region RB may be trapezoidal with the side on the gap region RG side as the base.

[0044] As previously described, the intersection region R0 has four distinct regions R1 to R4, each with a high sound velocity. Here, the sound velocity can be defined as, for example, the speed at which the elastic wave of the mode used by the device 1 propagates through the piezoelectric body 3. However, when multiple regions are defined based on the shape of the IDT electrode 5, the relative magnitudes of the sound velocities in the multiple regions do not reverse depending on the specific mode of the elastic wave used. Therefore, it is not necessary to specify which mode of the elastic wave the sound velocity is.

[0045] The speed of sound in elastic waves is affected by the mass of the component (e.g., 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 speed of sound. On the other hand, if the thickness of the conductive layer constituting the IDT electrode 5 is constant, the greater the ratio of the conductive layer to the unit area, the greater the mass per unit area. Therefore, the speed of sound is lower in regions where the area ratio of the conductive layer constituting the IDT electrode 5 is large.

[0046] In the illustrated example, the width (length in the D1 direction) of the electrode finger 11 is not constant. This creates four distinct regions R1 to R4, each with a different sound velocity. These regions are arranged in the order of R1, R2, R3, and R4, moving from both sides of the crossing region R0 in the D2 direction towards the center. Furthermore, listing these regions in order from the region with the lowest sound velocity, we get R1, R2, R3, and R4. In other words, the region closer to the center has a higher sound velocity.

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

[0048] In this paragraph, the line connecting the midpoints of the lengths of the intersecting region R0 in the D2 direction is referred to as the centerline of the intersecting region R0. Two first regions R1 are, for example, the same in distance from the centerline of the intersecting region R0 (the distance from the centerline in the D2 direction) and the same in length in the D2 direction. The same is true for two second regions R2 and two third regions R3. For example, the center of the length of the fourth region R4 in the D2 direction lies on the centerline of the intersecting region R0.

[0049] The third region R3 has a greater length (width) in the D2 direction than any other region within the intersecting region R0. For example, the sum of the widths of the two third regions R3 may be 50% or more, 80% or more, or 90% or more of the width of the intersecting region R0. The relative widths of the other regions within the intersecting region R0 may be set as appropriate. In the illustrated example, the regions are arranged in order from largest to smallest width: the first region R1, the fourth region R4, and the second region R2.

[0050] Each of the first to fourth regions R1 to R4 is, for example, a rectangle with a longer side parallel to the D1 direction. However, each of the first to fourth regions R1 to R4 may have a shape other than a rectangle. For example, if the intersection region R0 is a parallelogram as described above, each of the first to fourth regions R1 to R4 may be a parallelogram with four sides parallel to the four sides of the intersection region R0. For the specific dimensions of the first to fourth regions R1 to R4, please refer to the details of the planar shape of the IDT electrode described later. Also, the degree of the velocity difference between the first to fourth regions R1 to R4 may be set as appropriate. For the degree of the velocity difference, please refer to the details of the planar shape of the IDT electrode that affects the velocity (described later).

[0051] The busbar region RB has a lower speed of sound than the first region R1, in other words, a lower speed of sound than any region in the crossover region R0. The gap region RG has a higher speed of sound than, for example, the fourth region R4, in other words, a higher speed of sound than any region in the crossover region R0. Since the gap region RG has a higher velocity than the fourth region R4, the area ratio occupied by the IDT electrode 5 is smaller in the gap region RG than in the fourth region R4. However, in Figure 1 (and other figures described later), the change in the width of the electrode finger 11 is exaggerated, resulting in a larger area ratio occupied by the IDT electrode 5 in the gap region RG than in the fourth region R4, which differs from the actual area ratio.

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

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

[0054] The third region R3 on the +D2 side is formed by the region where the tip-side main portion 11b of the first electrode finger 11A and the base-side main portion 11d of the second electrode finger 11B overlap in the propagation direction. Similarly, the third region R3 on the -D2 side is formed by the region where the base-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] The first region R1 on the +D2 side is formed by the region where the widened tip portion 11a of the first electrode finger 11A and the widened base portion 11e of the second electrode finger 11B overlap in the propagation direction. Similarly, the first region R1 on the -D2 side is formed by the region where the widened base portion 11e of the first electrode finger 11A and the widened tip portion 11a of the second electrode finger 11B overlap in the propagation direction.

[0056] As described above, in the third region R3, the main sections with a reference width overlap, whereas in the first region R1, the widened sections with a width greater than the reference width overlap. As a result, the area ratio occupied by the IDT electrode 5 is larger in the first region R1 than in the third region R3. Consequently, the speed of sound is lower in the first region R1 than in the third region R3.

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

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

[0059] As described above, in the third region R3, the main sections with a reference width overlap in the propagation direction. In the first region R1, the widened sections with a width greater than the reference width overlap in the propagation direction. On the other hand, in the second region R2, the main section and the widened section overlap in the propagation direction. As a result, the area ratio occupied by the IDT electrode 5 in the second region R2 is smaller than in the first region R1, and larger than in the third region R3. Consequently, the sound velocity in the second region R2 is higher than in the first region R1, and lower than in the third region R3.

[0060] The fourth region R4 is formed by the 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, the main portions having a reference width overlap, whereas in the fourth region R4, the narrow portions 11c having a width narrower than the reference width overlap. Therefore, the area ratio occupied by the IDT electrode 5 is smaller in the fourth region R4 than in the third region R3. Consequently, the speed of sound is higher in the fourth region R4 than in the third region R3.

[0061] In the gap region RG, the gap G1 at the tip of the first electrode finger 11A and the base portion 11f of the second electrode finger 11B overlap in the propagation direction. Figure 1 exaggerates that the width of the narrow portion 11c is narrower than the width of the main portion, but in reality, the width of the narrow portion 11c is greater than half the width of the base portion 11f (the reference width in the illustrated example). As previously described, in the fourth region R4, the narrow portions 11c overlap in the propagation direction. Therefore, the area ratio occupied by the IDT electrode 5 is smaller in the gap region RG than in the fourth region R4. Consequently, the sound velocity is higher in the gap region RG than in the fourth region R4 (and the first to third regions R1 to R3). However, contrary to the illustrated velocity profile, the sound velocity in the gap region RG may be lower than in the fourth region R4.

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

[0063] Furthermore, for example, multiple openings arranged in the D1 direction may be formed in the busbar. In this case, the area ratio of the IDT electrodes in the busbar region will not be 100%, and consequently, the speed of sound in the busbar region will increase. However, this can be considered a matter of which part of the IDT electrodes is defined as the busbar and the busbar region. For example, in a busbar having multiple openings as described above, the part located on the intersection region R0 side of the multiple 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 certain width (in the D1 direction), and consequently, a step is formed at the boundary between adjacent portions. More specifically, this step has, for example, a relatively short edge that extends roughly parallel to the D1 direction. From another perspective, in the velocity profile, the change in velocity changes in a step-like manner. In reality, due to manufacturing errors, the corners of the step may be rounded, or the short edge may be curved.

[0065] Unlike the illustrated example, at least one of the multiple parts (11a to 11f) may have a portion that extends with a constant width, while the width of the portion connecting to the adjacent part may change so that the step is smooth. That is, if the existence of multiple parts (11a to 11f) is evident from the portion that extends with a constant width, the boundaries between adjacent parts do not necessarily have to be clear. From another perspective, in a velocity profile, if the existence of multiple regions (R1 to R4) is evident from the range where the velocity is constant (in the D2 direction), the boundaries between adjacent regions do not necessarily have to be clear.

[0066] Furthermore, unlike the illustrated example, among the multiple parts (11a to 11f), a step or a bend in the lateral edge of the electrode finger 11 may be formed at the boundary between adjacent parts, as in the illustrated example, and the width of at least one of the adjacent parts may change over the entire length of that part. In other words, if the existence of multiple parts (11a to 11f) is clear because the boundaries of adjacent parts are clear, each part does not have to have a portion that extends with a constant width. From another viewpoint, in the velocity profile, if the boundary of adjacent regions is clear due to a step or bend in the velocity line, and therefore the existence of multiple regions (R1 to R4) is clear, each region does not have to have a range (D2 direction) where the velocity is constant.

[0067] (Examples of dimensions for each part of the electrode finger) The specific dimensions of each part (11a to 11f) of the electrode finger 11 may be set as appropriate. For example, as follows. In the following, the ratio of the width (D1 direction) of the electrode finger 11 to twice the pitch p (2p) (= width / 2p) may be referred to as the duty cycle.

[0068] The tip-side main portion 11b and the base-side main portion 11d occupy most of the length (in the D2 direction) of the electrode finger 11. For example, the combined length of the tip-side main portion 11b and the base-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 crossing region R0 in the D2 direction). The lengths of the tip-side main portion 11b and the base-side main portion 11d are generally equal. However, the base-side widening portion 11e is longer than the tip-side widening portion 11a, so the base-side main portion 11d is shorter than the tip-side main portion 11b.

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

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

[0071] The length of the widened tip 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 also 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 of the root-side widening portion 11e (in the D2 direction) 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, or 1p or less or 0.7p or less. The above upper and lower limits may be combined as appropriate. 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, or 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 combined as appropriate. In the above examples, the width of the second region R2 is given as an example of a size less than the width of the first region R1, but the width of the second region R2 may be larger than or equal to the width of the first region R1.

[0073] The width of the widened tip section 11a (in the D1 direction) and the width of the widened base section 11e are, for example, the same. However, they may be different. The duty cycle of the widths of these widened sections may be, for example, 0.50 or more, 0.55 or more, or 0.60 or more, provided that it is greater than the duty cycle of the base width, and may also be 0.80 or less, 0.75 or less, or 0.70 or less. The above upper and lower limits may be combined as appropriate. From another perspective, the width of the widened section may be, for example, 1.1 times or more, or 1.2 times or more, of the base width, and may also be 1.5 times or less, or 1.4 times or less, of the base width. The above upper and lower limits may be combined as appropriate.

[0074] The length of the narrow section 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 also be less than 3.0p, less than 1.5p, or less than 1.0p. The above upper and lower limits may be combined as appropriate.

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

[0076] The length of the root 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 also be 1.0p or less, 0.7p or less, or 0.5p or less. The above upper and lower limits may be combined as appropriate.

[0077] The width of the base section 11f (in the D1 direction) is, for example, the standard width (in other words, the same width as the main section) as previously described. However, the width of the base section 11f may be smaller than the standard width, or larger than the standard width. For example, the width of the base section 11f may be the same as the width of the base-side widening section 11e. In this case, the base-side widening section 11e may be considered to extend to the bus bar 9.

[0078] (Various configuration examples of substrates containing piezoelectric elements) The piezoelectric body 3, having an upper surface 3a on which the IDT electrode 5 is formed, may be, for example, part or all of a substrate. The configuration of the substrate may be in various forms, for example, a known configuration. Examples of substrate configurations are given below.

[0079] Figure 2 is a cross-sectional view showing the configuration of substrate 13A as a first example of a substrate. The illustrated cross-section corresponds to the cross-section along line II-II in Figure 1.

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

[0081] The piezoelectric material 3 is composed of, for example, a piezoelectric single crystal. Examples of materials that make up 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 material 3 may also be composed of polycrystalline material. The cut angle, planar shape, and various dimensions of the piezoelectric material 3 may be set as appropriate. For example, a piezoelectric material made of LT or LN may be of rotational Y-cut X-propagation. That is, the propagation direction of the elastic wave (D1 direction) and the X-axis may approximately coincide (for example, the difference between the two is ±10°). In this case, the inclination angle of the Y-axis with respect to the normal (D3 direction) of the upper surface 3a of the piezoelectric material 3 may be set as appropriate. The thickness of the piezoelectric material 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 above upper and lower limits may be combined as appropriate.

[0082] The support substrate 15 may contribute, for example, to improving the strength of the substrate 13A, compensating for changes in characteristics due to temperature changes (temperature compensation), and confining elastic waves to the piezoelectric body 3. Improved strength may be achieved, for example, by appropriately setting the thickness of the support substrate 15, which is made of a material having a certain degree of strength. Temperature compensation may be achieved, for example, by having a lower coefficient of thermal expansion of the support substrate 15 than that of the piezoelectric body 3. Confinement of elastic waves may be achieved, for example, by having a sound velocity higher than that of the piezoelectric body 3 (and / or the intermediate layer 17), and / or by having different acoustic impedances for the support substrate 15 and the intermediate layer 17.

[0083] The material and thickness of the support substrate 15 may be set appropriately in light of the above-mentioned objectives. 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 an aluminum oxide sintered body (Al2O3). The thickness of the support substrate 15 is, for example, 1p or more or 3p or more. Also, the thickness of the support substrate 15 is, for example, greater than the thickness of the piezoelectric body 3.

[0084] The intermediate layer 17 may contribute, for example, to improving the bonding strength between the piezoelectric element 3 and the support substrate 15, and to confining elastic waves to the piezoelectric element 3. The improvement in bonding strength may be achieved, for example, by selecting a material for the intermediate layer 17 that has a relatively high bonding strength with the piezoelectric element 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 element 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 element 3 (and / or the support substrate 15).

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

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

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

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

[0089] Figure 3 is a cross-sectional view showing the configuration of substrate 13B as a second example of a substrate. The illustrated cross-section corresponds to the cross-section along line II-II in Figure 1.

[0090] Substrate 13B is the same as substrate 13A described above, but with a multilayer film 19 provided in place of the intermediate layer 17. The multilayer film 19 has two or more acoustic films (six in the illustrated example) (first film 21A and second film 21B). The materials of the multiple layers of acoustic films are different from each other for adjacent acoustic films (overlapping with each other without other acoustic films in between) in the stacking direction. From another perspective, adjacent acoustic films have different acoustic impedances. As a result, for example, the reflectivity of elastic waves is relatively high at the interface between them. As a result, for example, leakage of elastic waves propagating through the piezoelectric body 3 is reduced. Note that the combination of the intermediate layer 17 and the support substrate 15 in substrate 13A in Figure 2 may be considered a type of multilayer film. In substrate 13B in Figure 3, the multilayer film may be defined to include the support substrate 15.

[0091] The number of different materials and the number of acoustic films in the multilayer film 19 can be set as appropriate. In the illustrated example, two types of acoustic films (first film 21A and second film 21B) are stacked alternately in three or more layers (more specifically, six layers). The materials of the acoustic films are also arbitrary. For example, the material of the first film 21A may be silicon dioxide (SiO2). The material of the second film 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 acoustic impedance of the first film 21A is lower than that of the second film 21B, for example. The thickness of the acoustic films can be set as appropriate, 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 composed of a low-sound-velocity film and a high-sound-velocity film, similar to the intermediate layer 17 and support substrate 15 of the substrate 3A in Figure 2. For example, the first film 21A may be made of a material with a lower sound velocity than the piezoelectric material 3 (e.g., SiO2 or Ta2O5). The second film 21B may be made of a material with a higher sound velocity than the piezoelectric material 3 (e.g., Si3N4).

[0093] Although not specifically shown in the figures, the substrate containing the piezoelectric element 3 may be in various forms other than those described above. For example, the substrate may be composed almost entirely of the piezoelectric element 3. From another viewpoint, the piezoelectric element 3 may be relatively thick. The substrate may also have a cavity beneath the relatively thin (e.g., 2p or less or 1p or less) piezoelectric element 3. Furthermore, the substrate may have a high-sound-velocity layer that overlaps the lower surface of the intermediate layer 17, which acts as a low-sound-velocity layer, separately from the support substrate 15, as shown in the substrate 13A of Figure 2. Contrary to the descriptions of substrates 13A and 13B, elastic wave confinement may be achieved by the high-sound-velocity layer overlapping the lower surface of the piezoelectric element 3.

[0094] (Other components of the elastic wave apparatus) Although not specifically shown in the figures, the elastic wave apparatus 1 may have an insulating protective film covering the upper surface 3a of the piezoelectric element 3 over the conductive layer including the IDT electrode 5. The protective film may, for example, contribute to reducing corrosion of the conductive layer and / or contribute to temperature compensation. 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 apparatus 1 may have an additional film that overlaps the upper or lower surface of the IDT electrode 5. The additional film, for example, overlaps all or part of the IDT electrode 5 and has a shape that fits within the IDT electrode 5 in a planar view. Such an additional film is made of, for example, an insulating material or metallic material that has different acoustic properties from the material of the IDT electrode 5, and contributes to improving the elastic wave reflection coefficient.

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

[0097] (Summary of the first embodiment) As described above, the elastic wave apparatus 1 has a piezoelectric body 3 and an IDT electrode 5. The piezoelectric body 3 has a first surface (upper surface 3a). The IDT electrode 5 is located on the upper surface 3a. The IDT electrode 5 also has 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 different potential from the plurality of first electrode fingers 11A and are arranged alternately with the plurality of first electrode fingers 11A in the elastic wave propagation direction (D1 direction). The apparatus 1 has an intersection region R0 where the plurality of first electrode fingers 11A and the plurality of second electrode fingers 11B overlap in the elastic wave propagation direction. The intersection region R0 has a first region R1 to a third region R3 (here, the one 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 in which the multiple first electrode fingers 11A and multiple second electrode fingers 11B extend (direction D2), and has a higher velocity of sound than the first region R1. The third region R3 is located closer to the center than the second region R2, and has a higher velocity of sound than the second region R2.

[0098] Therefore, spurious emissions can be reduced, for example. Specifically, for example, by configuring a first region R1 with a slower sound velocity at the D2 direction end of the intersecting region R0, the piston mode (or a similar mode; the same applies hereinafter) can be utilized. As a result, spurious emissions of the transverse mode can be reduced. Furthermore, by configuring a second region R2 with a sound velocity higher than the first region R1 and lower than the third region R3, spurious emissions can be further reduced. The applicant has confirmed this effect through measured values ​​in prototypes and simulation calculations, and will show some examples later. The reason why spurious emissions are reduced by the formation of the second region R2 is that, for example, the effect of reducing transverse mode spurious emissions is amplified by the configuration of two low-sound-velocity regions that contribute to the realization of the piston mode.

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

[0100] In this case, for example, the -D2 end of the widened tip portion 11a of the first electrode finger 11A and the -D2 end of the widened base portion e of the second electrode finger 11B will be at different positions in the D2 direction. As a result, the reflection position and / or diffraction position of the elastic wave propagating in the transverse direction will differ depending on the position in the D1 direction. Consequently, the probability of transverse elastic waves reinforcing each other is reduced, and spurious emissions are reduced. Furthermore, for example, it is easy to realize a second region R2 in which the speed of sound is higher than that of the first region R1 and lower than that of the third region R3. More specifically, for example, it is as follows. In a different embodiment from this one, 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 embodiment is also included in the technology of this disclosure). In this embodiment, it may be difficult to achieve such a width for the second region R2 due to the machining accuracy of the width of the electrode finger 11. However, in this embodiment, the second region R2 can be achieved even in such cases.

[0101] The widened portions located on the tip side of the multiple first electrode fingers 11A (tip-side widened portions 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 located on the base side of the multiple second electrode fingers 11B (base-side widened portions 11e) may be located in the first region R1 on the +D2 side and the second region R2 on the +D2 side. That is, the base-side widened portions 11e may extend further towards the center in the D2 direction of the crossing region R0 than the tip-side widened portions 11a.

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

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

[0104] In this case, for example, spurious emissions can be further reduced. The applicant has confirmed this effect through measured values ​​and simulation calculations in prototypes, and will show some examples later. The reason why spurious emissions are reduced by the formation of the fourth region R4 is that, for example, the effect of reducing lateral mode spurious emissions is amplified by the configuration of multiple velocity profiles that contribute to the realization of the piston mode.

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

[0106] In this case, for example, the characteristics of the elastic wave apparatus 1 are improved. The applicant has confirmed this effect through measured values ​​and simulation calculations in prototypes, and will show some examples later. The reason why the characteristics are improved when the width of the fourth region R4 is less than 1.5p is that, for example, a shorter width in the fourth region R4 makes it easier to secure the width of the third region R3, which is responsible for the basic characteristics. Another example is that a transverse mode elastic wave having a wavelength (2p) equivalent to the elastic wave intended for use does not fit within the fourth region R4.

[0107] The elastic wave apparatus 1 may further include a low-sound-velocity membrane (intermediate layer 17 in Figure 2 or first membrane 21A in Figure 3) and a high-sound-velocity membrane (support substrate 15 in Figure 2 or second membrane 21B in Figure 3). The low-sound-velocity membrane overlaps the piezoelectric body 3 on the opposite side of the upper surface 3a and has a lower sound velocity than the piezoelectric body 3. The high-sound-velocity membrane overlaps the low-sound-velocity membrane on the opposite side of the piezoelectric body 3 and has a higher sound velocity than the piezoelectric body 3.

[0108] In this case, for example, the elastic waves leaking from the piezoelectric element 3 can be reduced. As a result, the characteristics of the device 1 are improved.

[0109] <Second Embodiment> Figure 4 is a plan view showing the configuration of the elastic wave apparatus 201 (hereinafter sometimes referred to as "apparatus 201") according to the second embodiment. Figure 5 is a cross-sectional view taken along the VV line in Figure 4.

[0110] In Figure 4, for convenience, hatching is applied to the upper surfaces (i.e., non-cross-sectional surfaces) of the first and second additional films 23A and 23B, which will be described later. Also, in Figure 4, for convenience, some of the reference numerals related to the IDT electrode 205 are applied to parts that are covered and not visible by the aforementioned additional films. Contrary to the following explanation, the additional films may be considered as part of the IDT electrode 205.

[0111] In the description of the first embodiment, it was stated that the sound speed of an elastic wave is affected by the mass of a component (e.g., IDT electrode 5) located on the upper surface 3a of the piezoelectric body 3. In the first embodiment, the mass on the upper surface 3a in the first region R1 to the fourth region R4 is made different by changing the width of the electrode finger 11, and consequently, the velocity profile shown in Figure 1 is realized. In the second embodiment, instead of changing the width of the electrode finger 11, the velocity profile shown in Figure 1 is realized by providing additional films (first additional film 23A and second additional film 23B) that partially overlap the electrode finger 11. Specifically, it is as follows.

[0112] The IDT electrode 205, like the IDT electrode 5 of the first embodiment, has a pair of comb-shaped electrodes 207. The pair of comb-shaped electrodes 207 has a busbar 9 and a plurality of electrode fingers 211 (a plurality of first electrode fingers 211A and 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 along their entire length.

[0113] The first additional film 23A and the second additional film 23B are superimposed in order on the IDT electrode 205. The first additional film 23A overlaps the portion of the electrode finger 211 corresponding to the tip-side widened portion 11a, tip-side main portion 11b, base-side main portion 11d, and base-side widened portion 11e of the electrode finger 11 in the first embodiment. The second additional film 23B overlaps the portion of the electrode finger 211 corresponding to the tip-side widened portion 11a and base-side widened portion 11e of the electrode finger 11 in the first embodiment. As a result, the first region R1 to the fourth region R4, which have a velocity profile similar to the velocity profile in Figure 1, are realized, similar to the first embodiment.

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

[0115] Furthermore, in the illustrated example, the first additional membrane 23A and the second additional membrane 23B overlap the busbar 9. Unlike the illustrated example, the first additional membrane 23A and / or the second additional membrane 23B do not necessarily overlap the busbar 9. Note that the presence or absence of the first additional membrane 23A and the second additional membrane 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 addition film was also mentioned in the description of the first embodiment. The description of the addition film in the first embodiment may be applied to this embodiment. For example, unlike the illustrated example, the addition film may be located on the lower surface of the IDT electrode 5. The specific material and thickness of the addition film are arbitrary. For example, when the material of the addition film is an insulating material, examples include Ta2O5, TaSi2, W5Si2, WC, and TiN. The thickness of the addition film may be, for example, 0.01p or more and 0.2p or less.

[0117] As described above, in this embodiment as well, the intersection region R0 of the elastic wave device 201 has a first region R1 to a third region R3. Therefore, the same effects as in the first embodiment are 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) that overlaps both the plurality of first electrode fingers 211A and the plurality of second electrode fingers 211B. The second region R2 on the +D2 side may have a second additional film 23B that overlaps either one of the plurality of first electrode fingers 211A or the plurality of second electrode fingers 211B (the second electrode fingers 211B), and may not have a second additional film 23B that overlaps the other (the first electrode fingers 211A). The third region R3 may not have a second additional film 23B on either the plurality of first electrode fingers 211A or the plurality of second electrode fingers 211B.

[0119] In this embodiment, where regions with different sound velocities are realized by the addition of a film, the likelihood of short circuits due to widening of the electrode fingers 11 and / or increased resistance due to narrowing of the electrode fingers 11 is reduced. As a result, it is easy to increase the difference in sound velocities between regions. Furthermore, compared to the second embodiment, the first embodiment does not provide an addition film, thus reducing the number of required materials and simplifying the manufacturing process. Consequently, costs can be reduced.

[0120] <Third Embodiment> Figure 6 is a plan view showing the configuration of the elastic wave apparatus 301 (hereinafter sometimes simply referred to as "apparatus 301") according to the third embodiment.

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

[0122] The 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 busbar 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 root-side main portion 311d, a root-side widened portion 311e, and a root 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 in parallel from the busbar 9 with a plurality of electrode fingers 311. The tip of the dummy electrode 25 of one comb-tooth electrode 307 faces the tip of the electrode finger 311 of the other comb-tooth electrode 307 via a gap G1. Note that, unlike the first embodiment, the root 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] Due to the provision of multiple dummy electrodes 25, a dummy region RD is formed between the gap region RG and the busbar region RB. The speed of sound in the dummy region RD is lower than the speed of sound in the gap region RG and higher than the speed of sound in the busbar region RB, assuming the addition film is not considered. However, this relationship may differ depending on the addition film. For the purposes of this description, the addition film will be disregarded.

[0125] The shape of the dummy electrode 25 (or, from another perspective, the sound velocity in the dummy region RD) may be set as appropriate. In the illustrated example, the shape of the dummy electrode 25 is generally such that it protrudes in a direction perpendicular to the propagation direction of elastic waves with a constant width. Also, in the illustrated example, the width of the dummy electrode 25 is the same as the reference width of the electrode finger 311 (width of the main part 19a on the tip side, etc.). From another perspective, the sound velocity in the dummy region RD is equivalent to the sound velocity 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 widened tip portion 311a. In this case, the width of the base portion 311f may be the same as or different from the width of the widened tip portion 311a. Also, from another point of view, the speed of sound in the dummy region RD may be lower or higher than the speed of sound in the third region R3. For example, the speed of sound in the dummy region RD may be the same as the speed of sound in the first region R1 or the second region R2.

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

[0128] As described above, in this embodiment as well, the intersection region R0 of the elastic wave device 301 has a first region R1 to a third region R3. Therefore, the same effects as in the first embodiment are 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 busbar 9) as the plurality of first electrode fingers 311A, and their tips face the tips of the plurality of second electrode fingers 311B via a gap G1. The plurality of second dummy electrodes 25B are connected to the same potential (same busbar 9) as the plurality of second electrode fingers 311B, and their tips face the tips of the plurality of first electrode fingers 311A ​​via a gap G1.

[0130] In this case, for example, in addition to having three or more regions with different sound velocities within the intersection region R0, the number of regions with different sound velocities also increases outside the intersection region R0. That is, the number of adjustment parameters for the velocity profile increases. As a result, it becomes easier to reduce spurious emissions that cannot be reduced by adjusting the velocity profile within the intersection region R0 alone.

[0131] <Other embodiments of acoustic wave devices> Although not specifically shown in the figures, the elastic wave apparatus according to this disclosure may be realized in various forms other than the first to third embodiments. For example, as follows:

[0132] The thickness of the IDT electrode can 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 added film in the third embodiment may be a change in the thickness of the IDT electrode itself.

[0133] Furthermore, the change in the width of the electrode fingers in the first embodiment, the presence or absence of the additional film in the second embodiment, and the change in the thickness of the electrode fingers can be conceptually understood as a change in the mass per unit length in the direction in which the electrode fingers extend, of the mass on the region of the upper surface 3a of the piezoelectric body 3 where the electrode fingers overlap. For convenience, in the following explanation, the portion of the electrode fingers in which the mass per unit length changes relative to the reference portion of the electrode fingers (for example, the main portion located in the third region) may be referred to as the mass change portion.

[0134] When at least the lower surface of the additional film (see Third Embodiment) is insulating, the additional film may be located not only in a position overlapping the multiple electrode fingers, but also between the multiple 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 extended in the D1 direction while maintaining the same range in the D2 direction as in the Third Embodiment.

[0135] In this embodiment, the second region R2 is realized by providing widening portions or additional membranes (mass-changing portions) every other in an arrangement of multiple first electrode fingers and multiple second electrode fingers. However, as mentioned in the description of the first embodiment, the second region R2 may also be realized by making the width of all electrode fingers equal to the 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-changing portions such as additional membranes.

[0136] The method of providing alternating mass change sections (such as widening sections) in the second region R2 may also be applied to other regions other than the second region R2. Furthermore, the method of providing alternating mass change sections may be applied not only when increasing the mass of a reference part of the electrode finger (for example, the main part located in the third region), but also when decreasing the mass. For example, in the fourth region of the first embodiment, the narrowing sections 11c may be provided every other finger. Also, the mass change sections may be provided every two or more electrodes rather than every other electrode finger.

[0137] The various methods described above for varying the mass on the upper surface 3a of the piezoelectric body 3 across multiple regions may be combined as appropriate. For example, a widened portion may be provided on the electrode finger, and an additional film may be provided that overlaps the widened portion but does not overlap the main portion. Alternatively, for example, a narrowed portion may be provided without a widened portion, and an additional film may be provided only in the first region R1 and the second region R2 of the first to fourth regions R4.

[0138] There may be three types of regions located within the intersection region R0 that have different sound velocities. For example, the second region R2 may be omitted. Specifically, taking the first embodiment as an example, the length of the tip-side widening portion 11a and the length of the root-side widening portion 11e may be the same. Also, for example, the fourth region R4 may be omitted. Taking the first embodiment as an example, the narrow portion may not be provided, and the tip-side main portion 11b and the root-side main portion 11d may be connected to form a single main portion.

[0139] In the embodiments, the first to fourth regions R1 to R4 are examples of the first to fourth regions in this disclosure. However, in embodiments where the second region R2 is omitted, the third region R3 may be considered an example of the second region, and the fourth region R4 may be considered an example of the third region. Also, in embodiments, two adjacent regions from the first to fourth regions R1 to R4 may be considered an example of one of the first to third regions.

[0140] Conversely, there may be five or more regions located within the intersection region R0 that have different speeds of sound. For example, a fifth region may be provided between the second region R2 and the third region R3, where the speed of sound is higher than that of the second region R2 and lower than that of the third region R3. However, in this case, the second region R2 and the fifth region may be considered as examples of the second region, or the fifth region and the third region R3 may be considered as examples of the third region.

[0141] In this embodiment, three or more regions are provided within the intersection region R0 such that the sound velocity increases towards the center in the D2 direction. However, at least one region that does not follow the relationship that the sound velocity increases towards the center in the D2 direction may be inserted between these three or more regions. Such regions may be used, for example, to fine-tune the characteristics of the elastic wave apparatus.

[0142] Furthermore, from this disclosure, it is possible to extract a higher-level concept in which three or more regions with different sound velocities are provided within the intersection region R0. In this higher-level concept, it is not essential that the three or more regions are provided such that the sound velocity increases towards the center in the D2 direction.

[0143] <Examples of use of elastic wave equipment> Elastic wave devices can be used in various forms, such as resonators and filters. Examples of elastic wave device applications are shown below. Specifically, they will be explained in roughly the following order. • An example of a resonator • An example of a signal splitter • Example of a communication device

[0144] The resonator, demultiplexer, and communication device are all examples of the use of elastic wave devices. The description of the demultiplexer also includes an example of a filter as an example of the use of an elastic wave device. In the following description, the elastic wave device 1 of the first embodiment will be used as an example of an elastic wave device. However, other elastic wave devices may be used, of course.

[0145] (An example of a resonator) Figure 7 is a plan view showing the configuration of the resonator 31.

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

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

[0148] The pair of reflectors 35 are made of the same conductive layer as the conductive layer constituting the IDT electrode 5, for example. In an embodiment 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 reflectors 35 may be provided. The pair of reflectors 35 are located on both sides of the IDT electrode 5 in the direction of elastic wave propagation. Each reflector 35 may be electrically floating, for example, or a reference potential may be applied to it.

[0149] Each reflector 35 is formed, for example, in a grid pattern. That is, each reflector 35 includes a pair of busbars 37 facing each other and a plurality of strip electrodes 39 extending between the pair of busbars 37. Similar to the plurality of electrode fingers 11, the number of strip electrodes 39 may actually be greater than the number shown.

[0150] Busbar 37 has a configuration that is generally similar to, for example, busbar 9 of the IDT electrode 5, and the description of busbar 9 can be applied to busbar 37. Busbar 37 is arranged in series with respect to busbar 9 in the direction of elastic wave propagation. The width of busbar 37 is also set to be the same as the width of busbar 9.

[0151] Unlike the illustrated example, the width of busbar 37 may differ from the width of busbar 9. Busbar 37 may be located at a different position in the D2 direction from busbar 9. When busbar 9 is inclined in the direction of elastic wave propagation, busbar 37 may be inclined similarly to busbar 9, or it may be parallel to the direction of elastic wave propagation.

[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 they are suspended over a pair of busbars 37. The description of the electrode fingers 11 may be adapted to the strip electrodes 39 as appropriate. The multiple strip electrodes 39 are arranged in the direction of elastic wave propagation, following the arrangement of the multiple electrode fingers 11. The pitch of the multiple strip electrodes 39, as well as the pitch between the electrode fingers 11 adjacent to the reflector 35 and the strip electrodes 39 adjacent to the IDT electrode 5, is, for example, equivalent to the pitch of the multiple electrode fingers 11.

[0153] The specific planar shape of the strip electrode 39 (or, from another perspective, the change in width (length in the D1 direction) depending on 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 the region extended in the D1 direction from the first region R1 (see Figure 1, etc.). The width of the portion other than the widened portion 39b is, for example, equivalent to the reference width of the electrode finger 11 (width of the main tip portion 11b, etc.). The width of the widened portion 39b is, for example, equivalent to the width of the tip-side widened portion 11a and the base-side widened portion 11e of the electrode finger 11. Depending on the planar shape of the strip electrode 39 as described above, although not specifically indicated by symbols, two (three) regions with different sound velocities are formed in the region extended from the intersection region R0 (see Figure 1, etc.) to the reflector 35.

[0154] Unlike the illustrated example, the region extending from the intersection region R0 to the reflector 35 may have three or more regions with different sound velocities. For example, multiple strip electrodes 39 may be configured such that two types of widened sections with different lengths in the D2 direction are arranged alternately, similar to the electrode fingers 11. Also, multiple strip electrodes 39 may have a narrowed section towards the center in the D2 direction, similar to the electrode fingers 11. Two types of widened sections and narrowed sections may be combined. Conversely, the region extending from the intersection region R0 to the reflector 35 may have a constant sound velocity. That is, the strip electrode 39 may have a constant width along its length. As can be seen from the illustrated example, the number and types of sound velocity regions in the IDT electrode 5 and the number and types of sound velocity regions in the reflector 35 may be different (as in the illustrated example) or the same.

[0155] In the reflector 35, as with 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, but may be any other method. In a single resonator 31, the method for changing the mass may be the same for the IDT electrode 5 and the reflector 35 (as shown in the illustration), or it may be different.

[0156] (An example of a signal splitter) Figure 8 is a schematic circuit diagram showing the configuration of a demultiplexer 101 (e.g., a duplexer). As can be understood from the symbols shown in the upper left of the figure, the comb-tooth electrodes 7 are schematically represented by a bifurcated fork shape, and the reflector 35 is represented by a single line with bent ends.

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

[0158] The transmitting filter 109 is configured as a ladder filter, for example, in which multiple resonators 31 (series resonators 31S and parallel resonators 31P) are connected in a ladder configuration. That is, the transmitting filter 109 has multiple (or even just one) series resonators 31S connected in series between the transmitting terminal 105 and the antenna terminal 103, and multiple (or even just one) parallel resonators 31P (parallel arms) connecting the series line (series arm) to the reference potential section (notation omitted).

[0159] The receiving filter 111 is composed of, for example, a resonator 31 and a multimode filter (including a doublemode filter) 113. The multimode filter includes a doublemode filter. The multimode filter 113 has a plurality of (three in the illustrated example) IDT electrodes 5 arranged in the direction of elastic wave propagation and a pair of reflectors 35 positioned on either side thereof.

[0160] At least one of the multiple resonators of the transmitting filter 109 (ladder filter) may include an elastic wave device 1 (IDT electrode 5) according to the embodiment. In terms of representation with respect to one IDT electrode 5 of the device 1, the transmitting filter 109 has the device 1 and one or more other IDT electrodes (in the illustrated example, the other IDT electrodes are also IDT electrodes 5 according to the first embodiment) located on the upper surface 3a of the piezoelectric body 3 of the device 1 and connected in a ladder-like manner to the one IDT electrode 5 to constitute a ladder filter.

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

[0162] Furthermore, the demultiplexer 101, the transmit filter 109 (ladder filter), the receive filter 111, and the multiple mode filter 113 may be considered as being part of the apparatus 1 according to the first embodiment, or as being included in the apparatus 1.

[0163] The multiple IDT electrodes 5 (and reflectors 35) of the demultiplexer 101 may be provided on one piezoelectric body 3 (substrate), or they may be distributed across two or more piezoelectric bodies 3. For example, the multiple resonators 31 constituting the transmitting filter 109 may be provided on the same piezoelectric body 3. Similarly, the resonators 31 constituting the receiving filter 111 and the multimode filter 113 may be provided on the same piezoelectric body 3, for example. The transmitting filter 109 and the receiving filter 111 may be provided on the same piezoelectric body 3, for example, 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 other identical piezoelectric bodies 3.

[0164] Figure 8 is merely one example of the configuration of the decoupler 101. Therefore, for example, the receiving filter 111 may be configured as a ladder-type filter, similar to the transmitting filter 109. Also, the transmitting filter 109 may have a multiple-mode filter 113. The decoupler 101 is not limited to a duplexer; for example, it may be a diplexer or a multiplexer containing three or more filters.

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

[0166] In the communication device 151, the transmission information signal TIS, which contains the information to be transmitted, is modulated and its frequency is boosted (converted to a high-frequency signal with a carrier frequency) by the RF-IC (Radio Frequency Integrated Circuit) 153 to become the transmission signal TS. The transmission signal TS has unwanted components other than the transmission passband removed by the bandpass filter 155, is amplified by the amplifier 157, and input to the demultiplexer 101 (transmission terminal 105). The demultiplexer 101 (transmission filter 109) then removes unwanted components other than the transmission passband from the input transmission signal TS, and outputs the transmission signal TS after removal from the antenna terminal 103 to the antenna 159. The antenna 159 converts the input electrical signal (transmission signal TS) into a radio signal (radio wave) and transmits it.

[0167] Furthermore, in the communication device 151, the radio signal (radio wave) received by the antenna 159 is converted into an electrical signal (received signal RS) by the antenna 159 and input to the demultiplexer 101 (antenna terminal 103). The demultiplexer 101 (receive filter 111) removes unwanted components other than the passband for reception from the input received signal RS and outputs it to the amplifier 161 from the receiving terminal 107. The output received signal RS is amplified by the amplifier 161, and unwanted components other than the passband for reception are removed by the bandpass filter 163. Then, the received signal RS is frequency-downgraded and demodulated by the RF-IC 153 to become the received information signal RIS.

[0168] The transmitted information signal TIS and the received information signal RIS may be low-frequency signals (baseband signals) containing appropriate information, such as analog or digitized audio signals. The passband of the radio signal may be set as appropriate and may conform to various known standards. The modulation scheme may be phase modulation, amplitude modulation, frequency modulation, or a combination of two or more of these. The circuit scheme is exemplified as a direct conversion scheme, but may be any other appropriate scheme, such as a double superheterodyne scheme. Furthermore, Figure 9 schematically shows only the essential parts, and low-pass filters, isolators, etc. may be added at appropriate positions, or the positions of amplifiers, etc. may be changed.

[0169] Furthermore, the elastic wave device 1 may be used in various forms other than those exemplified above. For example, the elastic wave device 1 may be used in a two-port resonator or in a transversal filter.

[0170] <Examples> The effectiveness of the elastic wave apparatus 1 according to the embodiment was confirmed by measuring the characteristics of a prototype of the resonator 31 (Figure 7) according to the embodiment and by calculating the characteristics of the resonator 31 through simulation. Several examples are shown below.

[0171] (Comparative Example 1 and Example 1) Figure 10 shows the characteristics of the resonator according to the first comparative example and the first embodiment.

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

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

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

[0175] As shown in Figure 10, in the first embodiment, the number and magnitude of spurious emissions were reduced compared to the first comparative example. Specifically, it was confirmed by measured values ​​that spurious emissions were 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: Material:LT Cut angle: 50° rotation Y-cut X-propagation Thickness: 0.65 μm ·Low sound velocity layer (middle layer 17): Material: SiO2 Thickness: 0.22 μm ·High sonic layer (support substrate 15): Material:Si Thickness: Sufficient thickness relative to pitch p (200 μm) ·IDT electrode: Material: Laminated structure of Ti and Al Thickness: Ti: 60 Å Al: 1400 Å Electrode finger: Number of bottles: 250 Pitch: 1.03 μm Width of the crossover region R0: 40p ·Reflector: Material and thickness: Same as IDT electrodes Strip electrodes: Number of reflectors: 30 (1 reflector) Pitch: Same as the pitch of the electrode fingers.

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

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

[0179] (Second Comparative Example and First Example) Figure 11 shows the characteristics of the resonators related to the second comparative example and the first embodiment (described above), and is similar to Figure 10.

[0180] Figure 11, like Figure 10, was obtained by measuring the characteristics of the prototype. In Figure 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 Figure 10.

[0181] In the electrode finger of the second comparative example, unlike the electrode finger 11 of the first embodiment, the widened portion at the tip and the widened portion at the base have the same length in the D2 direction. Also, the electrode finger of the second comparative example does not have a narrowed portion. That is, in the second comparative example, similar to IDT electrodes that use a general piston mode, the intersection region has only two (three) regions with different sound velocities. Also, the strip electrode of the reflector of the second comparative example has a constant width (reference width) along its entire length, similar to the strip electrode of the reflector of the first comparative example. Other conditions are generally the same for the first comparative example and the first embodiment.

[0182] As shown in Figure 11, in the first embodiment, the number and magnitude of spurious emissions were reduced compared to the first comparative example. Specifically, it was confirmed by measured values ​​that spurious emissions were reduced by forming the first region R1 to the fourth region R4 within the intersection region R0.

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

[0184] (Second example) Figure 12 shows the characteristics of the resonators for the first comparative example and the second comparative example (both described above), as well as the second embodiment, and is similar to Figure 10.

[0185] Unlike Figures 10 and 11, Figure 12 was obtained through simulation calculations. In Figure 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 numerals (LC1 and LC2) as in Figures 10 and 11.

[0186] The second embodiment is the same as the first embodiment but without the narrow section 11c. That is, in the second embodiment, the intersection region does not have a fourth region R4, but has three (five) regions with different sound velocities (corresponding to the first region R1 to the third region R3). The other configurations of the second embodiment are the same as those of the first embodiment.

[0187] As shown in Figure 12, in the second embodiment, the magnitude of spurious emissions is reduced compared to the first and second comparative examples. Specifically, simulation calculations confirmed that spurious emissions are 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 perspective, without forming the fourth region R4).

[0188] (Third embodiment) Figure 13 shows the characteristics of the resonators for the first comparative example, the second comparative example (both described above), and the third embodiment, and is similar to Figure 10.

[0189] Figure 13, like Figure 12, was obtained by simulation calculation. In Figure 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 Figure 12. Line LE3 shows the characteristics of the third embodiment.

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

[0191] As shown in Figure 13, in the third embodiment, the magnitude of spurious emissions is reduced compared to the first and second comparative examples. Specifically, simulation calculations confirmed that spurious emissions are 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 a fourth region R4 (or, from another perspective, without forming the second region R2).

[0192] (Examples 4 to 7) Figure 14 shows the characteristics of the resonators according to the 4th to 7th embodiments, and is similar to Figure 10.

[0193] Figure 14, like Figure 12, was obtained by simulation calculations. In Figure 14, lines LE4, LE5, LE6, and LE7 represent the characteristics of the fourth, fifth, sixth, and seventh embodiments.

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

[0195] Within the range of the width of the fourth region R4 described above, generally, the smaller the width, the smaller the spurious emission. In Figure 14, lines LE4 to LE7 overlap and are difficult to compare, so the impedance phase (°) for each embodiment in spurious emissions S1 to S4 in the figure is shown below. The larger the value shown below, the smaller the spurious emission. 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...Elastic wave device, 3...Piezoelectric material, 3a...Top surface (first surface), 5...IDT electrode, 11A...First electrode finger, 11B...Second electrode finger, R0...Crossing region, R1...First region, R2...Second region, R3...Third region.

Claims

1. A piezoelectric material having a first surface, The IDT electrode located on the first surface, Equipped with, The IDT electrode is Multiple first electrode fingers, It has a plurality of second electrode fingers connected to a different potential from the plurality of first electrode fingers and arranged alternately with the plurality of first electrode fingers in the elastic wave propagation direction, In the direction of elastic wave propagation, the intersection region where the plurality of first electrode fingers and the plurality of second electrode fingers overlap, It has, The aforementioned crossing region has a plurality of regions, each having a length in the first direction in which the plurality of first electrode fingers and the plurality of second electrode fingers extend, which can be distinguished by differences in the speed of sound. The aforementioned multiple regions are, A first region having a first sound velocity is located on the tip side of the plurality of first electrode fingers or plurality of second electrode fingers in the first direction, Located towards the center in the first direction from the first region, having a third sound velocity higher than the first sound velocity, and having a length in the first direction that is the largest of the multiple regions, It has a fourth region located towards the center in the first direction from the third region and having a fourth sound velocity higher than the third sound velocity, Elastic wave device.

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

3. The third region is located on both sides of the fourth region, and the sum of the lengths of the third region in the first direction is 50% or more of the length of the intersecting region in the first direction. The elastic wave apparatus according to claim 1.

4. The first region is located on both sides of the third region, The length of the first region in the first direction is greater than the length of the fourth region in the first direction. The elastic wave apparatus according to claim 1.

5. The fourth region is located in the center of the intersection region in the first direction. The elastic wave apparatus according to claim 1.

6. Multiple first dummy electrodes are connected to the same potential as the multiple first electrode fingers, and their tips face the tips of the multiple second electrode fingers with a gap between them, Multiple second dummy electrodes are connected to the same potential as the plurality of second electrode fingers, and their tips face the tips of the plurality of first electrode fingers with a gap between them, The elastic wave apparatus according to claim 1, further comprising the following:

7. The elastic wave apparatus according to claim 1, One or more other IDT electrodes located on the first surface and connected in a ladder-like manner to the IDT electrode to constitute a ladder-type filter, A filter that has the following properties.

8. The elastic wave apparatus according to claim 1, One or more other IDT electrodes located on the first surface and arranged in the direction of elastic wave propagation relative to the IDT electrode to constitute a multimode filter, A filter that has the following properties.

9. Antenna terminal and A transmitting filter connected to the aforementioned antenna terminal, A receiving filter connected to the aforementioned antenna terminal, It has, At least one of the transmitting filter and the receiving filter is configured by the filter according to claim 7 or 8. Duplexer.

10. The demultiplexer according to claim 9, The antenna connected to the aforementioned antenna terminal, ICs connected to the transmit filter and the receive filter, A communication device that has the following features.

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