JP2007013414A - Surface acoustic wave element strip, surface acoustic wave device, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave element strip capable of obtaining a high Q value while maintaining the thickness of an electrode layer thickness constituting an IDT (interdigital transducer), when it is used for a SAW (surface acoustic wave) device. <P>SOLUTION: A surface acoustic wave element strip 10 comprises an IDT 14 having electrode fingers 22 arranged at a plate surface of a piezoelectric substrate 12 in a direction perpendicular to the travelling direction of a surface acoustic wave excited by the piezoelectric substrate 12. A plurality of adjoining electrode fingers 22 are made as one group, and a period length forming the electrode fingers 22 is changed periodically per group. The strip 10 adopts a configuration in which the IDTs 14 are put between reflectors 18a and 18b comprising a plurality of conductor strips arranged in a lattice shape. In addition, an electrode finger formation period length of a group unit consists of two period lengths for the surface acoustic wave element strip 10 employing the configuration, and it is desirable for the period length ratio to be within the range of 7:10 to 9:10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface acoustic wave element piece, a surface acoustic wave device, and an electronic apparatus, and in particular, the Q value of a surface acoustic wave element piece that has a high reflection coefficient by increasing the film thickness or line width of an electrode. The present invention relates to a technique suitable for improving the surface acoustic wave device, a surface acoustic wave device including the surface acoustic wave element according to the technology, and an electronic apparatus including the surface acoustic wave device.

  In forming a surface acoustic wave element (for example, one used as a resonator), by increasing the film thickness and line width of the electrode pattern formed on the plate surface of the piezoelectric substrate, a high reflection coefficient can be obtained and elasticity In the case of a surface acoustic wave device, it is known that good temperature characteristics can be obtained in a wide range. However, a surface acoustic wave element piece (Surface Acoustic Wave: SAW element piece) obtained with a high reflection coefficient by increasing the film thickness and line width of the electrode pattern has a property that the Q value is deteriorated. This is considered to be caused by a rapid increase in energy loss when the surface acoustic wave generated in the interdigital electrode formed on the plate surface of the piezoelectric substrate is mode-converted into a bulk wave.

Such a characteristic that the Q value decreases as the reflection coefficient increases can be seen not only when this SAW element piece is used as a SAW resonator but also when it is used as a filter. Patent Document 1 discloses a technique related to a SAW filter that lowers conductance characteristics for the purpose of preventing energy loss. In the SAW filter disclosed in Patent Document 1, the interval between electrode fingers of a pair of comb-shaped electrodes constituting an interdigital transducer (IDT) formed on a plate surface of a piezoelectric substrate is set for every half wavelength, that is, adjacent to each other. It is different periodically for each electrode finger.
JP-A-8-298432

  Patent Document 1 describes that the SAW element piece used as a surface acoustic wave filter has the above-described configuration, so that the conductance of the passband can be reduced and energy loss can be suppressed. .

  As described in Patent Document 1, when the electrode finger formation period length of the IDT constituting the SAW element piece is changed, it is possible to surely confirm the change in conductance characteristics, but at the same time, the amount of energy leakage Increases, and the Q value decreases.

  Accordingly, the present invention provides a surface acoustic wave element that can obtain a high Q value while keeping the film thickness of the electrode fingers constituting the IDT thick when used as a surface acoustic wave resonator or a surface acoustic wave filter. The purpose is to provide. It is another object of the present invention to provide a surface acoustic wave device equipped with a surface acoustic wave element capable of achieving the above object, and an electronic apparatus equipped with the surface acoustic wave device.

  In order to achieve the above object, it is considered that it is only necessary to confine energy lost due to a decrease in conductance value by means other than IDT. Accordingly, the surface acoustic wave element according to the present invention has interdigital electrodes having electrode fingers arranged on the surface of the piezoelectric substrate in a direction orthogonal to the traveling direction of the surface acoustic wave excited by the piezoelectric substrate. A surface acoustic wave element piece, in which a plurality of adjacent electrode fingers are set as one set, sets having different periodic lengths forming the electrode fingers are alternately arranged, and the interdigital electrodes are arranged in a lattice shape. Further, it is characterized in that it is sandwiched between reflectors having a plurality of conductor strips. According to the SAW element piece having such a configuration, the IDT electrode finger formation period length is periodically changed in units of groups, thereby maintaining the reflection coefficient in each electrode finger, in other words, while maintaining the electrode film thickness. The effective reflection coefficient as a whole can be reduced, and energy loss due to bulk wave radiation can be suppressed. Moreover, since the energy of the leakage from the IDT that has become insufficiently confined due to a decrease in the reflection coefficient can be confined by the reflector, energy loss as a whole element piece can be suppressed, and high Q value can be obtained.

  In the surface acoustic wave element having the above-described configuration, the electrode fingers that form each pair may be two electrode fingers that form pairs adjacent to each other that form comb-shaped electrodes. By adopting such a configuration, the periodic structure of the pair unit is not disturbed at the end portion of the IDT, and even a SAW element piece having an IDT with a small logarithm is effective.

  Further, in the surface acoustic wave element having the above-described configuration, the electrode finger formation period length of the pair unit is composed of two sets of period lengths, and the period length ratio between the sets is within the range of 7:10 to 9:10. It is desirable to do. By adopting such a configuration, the tendency of the reflection coefficient to decrease appears remarkably, and the effect of suppressing energy loss due to bulk wave radiation can be enhanced.

  Further, in the surface acoustic wave element having the above-described configuration, the interdigital electrode has a certain ratio between the line width of the electrode finger and the interval between the intermittent portions when the electrode finger is formed with a predetermined period length. Is desirable. By adopting such a configuration, temperature characteristics when used as a surface acoustic wave device can be stabilized.

  In order to achieve the above object, a surface acoustic wave device according to the present invention is characterized by mounting any one of the surface acoustic wave element pieces described above. The surface acoustic wave device having such a configuration can maintain good temperature characteristics in a wide band and has little energy loss.

  In addition, an electronic apparatus according to the present invention for achieving the above object is characterized by mounting the surface acoustic wave device having the above-described configuration. The electronic device having such a configuration can achieve high efficiency and high reliability.

  Hereinafter, embodiments of a surface acoustic wave element piece, a surface acoustic wave device, and an electronic apparatus according to the present invention will be described in detail with reference to the drawings. In addition, embodiment shown below is a form which shows a part of suitable embodiment of this invention, and this invention is not restrained by the following embodiment.

  FIG. 1 is a diagram showing an embodiment of a surface acoustic wave element according to the present invention. The SAW element piece 10 of this embodiment includes a piezoelectric substrate 12, an interdigital electrode (IDT) 14 disposed on the surface of the piezoelectric substrate 12, and a pair of reflectors 18 (18a, 18b) sandwiching the IDT 14. Is used as a SAW resonator or SAW filter.

The piezoelectric substrate 12 may be quartz (SiO ₂ ), lithium tantalate (LiTaO ₃ ), or the like. For example, quartz is preferably a plate body cut at a cut angle called ST cut.

  The IDT 14 includes a pair of comb-shaped electrodes 16 (16a, 16b). The comb-shaped electrode 16 is provided with a plurality of electrode fingers 22 formed vertically from a power supply conductor (bus bar) 20 and meshed so that the electrode fingers 22 provided on each bus bar 20 intersect at a predetermined interval. It has been. The IDT 14 is arranged so that the electrode fingers 22 of the comb-shaped electrode 16 are orthogonal to the propagation direction of the surface acoustic wave.

  The reflector 18 is composed of a plurality of conductor strips 24 whose ends are connected to each other, and has a lattice shape. The reflector 18 is disposed so that the plurality of conductor strips 24 are parallel to the electrode fingers 22 of the comb-shaped electrode 16, that is, perpendicular to the propagation direction of the surface acoustic wave.

  In the case of this embodiment, the electrode patterns such as the IDT 14 and the reflector 18 are made of a thin film of aluminum or an aluminum alloy. The electrode pattern is formed by forming a thin film of aluminum or aluminum alloy on the surface of the quartz substrate or quartz wafer by vapor deposition or sputtering and forming the thin film into a predetermined shape by photoetching. The IDT 14 is electrically connected to an electrode pad (not shown) so that power can be input and output.

  The first feature of the SAW element piece 10 of the present embodiment is that a pair is formed for each pair of adjacent electrode fingers 22 and the pitch between the electrode fingers 22 is periodically changed for each pair. Yes. More specifically, in FIG. 1, when the electrode period length (pitch) of the electrode fingers 22 formed in the A section is PA, the electrode fingers 22 formed in the B section is PB, and the electrode fingers formed in the A section are PB. The electrode finger group formed at the pitch PA and the electrode finger group formed at the pitch PB are alternately arranged such that the pitch of 22 is again PA.

  The pitches PA and PB of the electrode fingers 22 can be calculated based on Equation 1 described later. Moreover, the temperature characteristic can be stabilized by determining the line width of the electrode finger 22 with respect to the pitch according to a predetermined metal ratio (metallization ratio). As shown in FIG. 1, by changing the pitch of two adjacent electrode fingers 22 as a set, the periodic structure of the set unit is not disturbed at the end of the IDT 14, and the SAW element having the IDT 14 with a small logarithm Even the piece 10 has effectiveness.

  As a suitable condition for determining the ratio PPT of the period length PA and PB of the electrode finger 22, it is concluded that PA: PB is preferably in the range of 10: 7 to 10: 9 from the data shown in detail below. Derived. At this time, there is no question as to which of PA and PB is used as a reference. For example, when PA is used as a reference, PB / PA = 0.7 to 0.9 can be indicated. In this case, PA / PB≈1.43 to 1.11.

  The adjustment of the electrode period length ratio PPT as described above is based on the assumption that the periodic structure propagation path is configured in the IDT portion as well as the reflector. If the reflection coefficient of the IDT is increased, the surface acoustic wave is changed to the bulk wave. It was invented based on the viewpoint that the energy loss (energy loss based on bulk wave radiation) due to the mode conversion of the above increases rapidly and causes the Q value to decrease. Based on the above-mentioned concept, by determining the period length ratio PPT between the pitches PA and PB of the electrode fingers in the comb-shaped electrode constituting the IDT as described above, the balance of the mass of the electrode pattern constituting the IDT can be improved. It is considered that when propagating a surface acoustic wave, conversion to the bulk wave mode, that is, bulk wave radiation is suppressed, and an increase in loss can be suppressed. That is, it is considered that the effective reflection coefficient of the entire IDT can be reduced while maintaining the reflection coefficient of each electrode finger, in other words, maintaining the film thickness of the electrode.

  However, by simply adjusting the electrode period length ratio PPT as described above to reduce the effective reflection coefficient of the entire IDT, when used as a SAW resonator or SAW filter, confinement is insufficient. As a result, the amount of leakage of energy increases. This means that as a result, energy loss increases and the Q value decreases.

  Therefore, the SAW element piece 10 of the present embodiment has a second feature that the loss is suppressed by obtaining an energy confinement effect by the reflectors 18a and 18b sandwiching the IDT 14, and the period length and the reflection of the electrode finger 22 are reflected. The number of the conductor strips 24 was increased while determining the ratio of the period of the conductor strips 24 of the vessel 18 according to the following formula.

  As described above, the SAW element piece 10 according to the present embodiment reduces the effective reflection coefficient of the IDT 14 as a whole by adjusting the electrode period length ratio PPT, which is the first characteristic, and the reflection, which is the second characteristic. By reducing the loss due to the energy confinement by the vessel 18, a high Q value can be obtained while keeping the thickness of the metal thin film constituting the electrode finger 22 thick. That is, when used as a SAW resonator or SAW filter, a SAW element piece that has excellent temperature characteristics and can reduce loss can be obtained.

  Specific examples will be described below. The piezoelectric substrate used for the SAW element piece of this example is a quartz plate, and when the Euler angle display is (φ, θ, ψ), the cut angle is (0 °, θ, 0 ° ≦ | ψ | ≦ 90 °). That is, the quartz plate (piezoelectric substrate) 12 has a cut angle as shown in FIG. 2 in the quartz crystal. This cut angle is obtained as follows. When the electric axis of the crystal is the X axis, the mechanical axis is the Y axis, and the optical axis is the Z axis, the crystal plate 30 is a crystal perpendicular to the Z axis with Euler angles (0 °, 0 °, 0 °). It becomes a board. The coordinate axes newly obtained when the quartz plate 30 is rotated counterclockwise by the angle θ about the X axis as a rotation axis are defined as an X axis, a Y ′ axis, and a Z ′ axis. In this XY′Z ′ coordinate system, a new coordinate axis obtained by rotating the quartz plate 32 parallel to the plane formed by the X axis and the Y ′ axis by an angle ψ about the Z ′ axis is defined as the X ′ axis. , Y ″ axis and Z ′ axis. In this X′Y ″ Z ′ coordinate system, a crystal plate parallel to the surface formed by the X ′ axis and the Y ″ axis is a crystal plate with Euler angles (0 °, θ, ψ). In such a quartz crystal plate, the rotation angle θ about the X axis may be in the range of 0 ° ≦ θ ≦ 180 °, and preferably 95 ° ≦ θ ≦ 155 °. A suitable angle for ψ is in the range of 33 ° ≦ | ψ | ≦ 46 °. Therefore, a desirable quartz substrate as the piezoelectric substrate 12 in this embodiment has Euler angles (0 °, 95 ° ≦ θ ≦ 155 °, 33 ° ≦ | ψ | ≦ 46 °).

  The metallization ratio η with respect to the pitch of the electrode fingers 22 in the comb-shaped electrode 16 constituting the IDT 14 is preferably about 0.7 to 0.8. The thickness H of the thin film constituting the electrode is preferably in the range of H / λ = 0.09 to 0.11 when the wavelength of the surface acoustic wave excited by the piezoelectric substrate 12 is λ. This is because the temperature characteristics can be improved by setting the film thickness of the electrode in such a range.

  In the present embodiment, the number of electrode finger pairs: M, number of reflector conductors: N, cross finger width: WCR, electrode period length ratio: PPT = PB / PA, electrode finger reflection coefficient TANC0, reflection The description will be made assuming that the conductor conductor period length is PR, and the reflector conductor and IDT electrode finger period length ratio is PTN = PR / PA.

  First, the relationship between the characteristics of the radiation conductance G of the IDT 14 and the characteristics of the reflection coefficient Γ and the electrode period length ratio PPT will be described. FIG. 3 shows the characteristics of the radiation conductance G of the IDT 14 (FIG. 3A) and the characteristics of the reflection coefficient Γ of the IDT 14 (FIG. 3) when the number of electrode finger pairs M = 10 and the electrode period length ratio PPT = 0.810. (B)). FIG. 4 shows the characteristics of the radiation conductance G of the IDT 14 (FIG. 4A) and the characteristics of the reflection coefficient Γ of the IDT 14 when the electrode finger pair number M is 10 and the electrode finger cycle length ratio PPT is 0.999. It is a graph showing (FIG.4 (B)).

  As can be seen by comparing FIG. 3 and FIG. 4, the characteristic of the radiation conductance G of the IDT 14 shifts due to the change of the electrode period length ratio PPT, while the characteristic of the reflection coefficient Γ of the IDT 14 does not change, and the center It just shifts the frequency. From this relationship, an error occurs in the arrangement interval of the electrode fingers 22 due to the two-electrode periodic structure in which the electrode period length is periodically divided into PA and PB, and the arrangement of reflection and radiation is changed. It can be concluded that the characteristic of radiative conductance has changed.

  Based on this conclusion, the following hypothesis can be made. When the value of the radiation conductance G, which is the reciprocal of the inductance R, changes, the value of the inductance R also changes. For example, when the value of the inductance R increases, it can be considered that the energy in the IDT is not sufficiently confined and the leakage rate is large. That is, it can be considered that the effective reflection coefficient of the IDT as a whole has decreased. Considering these, when the value of the radiation conductance G or the value of the inductance R is increased by changing the electrode period length ratio PPT, the effective reflection coefficient of the IDT is decreased. Can think.

  Next, the setting of the pitch PA and PB in the electrode finger 22 of the comb-shaped electrode 16 constituting the IDT 14 for actually designing the SAW element piece 10 and the pitch PR of the reflector conductor will be described. FIG. 5 is a graph showing the relationship between the electrode cycle length ratio PPT and the deviation of the frequency deviation ft (ppm) of the IDT 14, and the horizontal axis indicates PPT and the vertical axis indicates the frequency deviation amount dft / f0 from the main resonance. . As can be seen from FIG. 5, the frequency deviation amount of the IDT 14 tends to decrease as the PPT approaches 1, and it can be said that the relationship is substantially proportional. FIG. 5 shows an example of a SAW element piece having a two-electrode finger periodic structure when the resonance frequency f0 = 312 MHz, the number of electrode finger pairs M = 90, and the number of reflector conductors N = 3.

  FIG. 6 is a graph showing the relationship between the reflection coefficient r of the reflector 18 and the deviation of the frequency deviation of the stop band of the reflector 18, wherein the horizontal axis represents the reflection coefficient r of the reflector 18 and the vertical axis represents the main resonance. Is shown as a frequency deviation amount dfr / f0. In FIG. 6, fu represents the upper limit of the stop band, fl represents the lower limit of the stop band, and fr represents the center frequency of the stop band. From FIG. 6, it can be seen that as the reflection coefficient increases, the center frequency of the stop band increases and the bandwidth of the stop band increases. FIG. 6 shows an example of the SAW element piece 10 having a two-electrode finger periodic structure when the resonance frequency f0 = 312 MHz, the number of electrode finger pairs M = 20, and the number of reflector conductors N = 2.

From the relationship of FIG. 5 and FIG. 6, ft and fr when PPT = 0.80, M = 90, and r = −0.15 are obtained, ft = 23,000 (ppm), fr = 47842 (ppm) Can be obtained. Here, if it is defined that frr = fr / f0 and ftr = ft / f0, the IDT electrode period lengths PA and PB and the reflector conductor period length PR can be calculated by the following equations, respectively.

とそれぞれの周期長を算出することができる。 Here, when V = 3244 (m / sec) and f0 = 312 MHz = 312 × 10 ⁶ , if a numerical value is appropriately substituted into the above Equation 1,

And the respective cycle lengths can be calculated.

  FIG. 7 shows electrode finger cycle lengths PA and PB, and reflector conductor cycle length PR according to the above-mentioned formula 1 for SAW element pieces with electrode finger pair number M = 90, reflector conductor number N = 3, and resonance frequency f0 = 312 MHz. 6 is a graph showing a shift in the maximum value of the radiation conductance G when the PPT is changed when calculating the value of. As can be seen from FIG. 7, it can be seen that the maximum value of the radiation conductance G decreases more in the range of PPT = 0.7 to 0.9 than in the case of PPT = 1. That is, when PPT = 0.7 to 0.9, it is considered that the effective reflection coefficient of the IDT 14 as a whole can be reduced at a large rate while ensuring the film thickness of the electrode finger 22. .

Next, with respect to the SAW element piece for which the values of the electrode finger cycle lengths PA and PB and the reflector conductor cycle length PR are calculated based on Formula 1, the energy is closed by the presence or absence of the reflector or the increase or decrease in the number N of the conductors of the reflector Examine the effects of intrusion. The design example 1 and the design example 2 of the SAW element piece are shown below, and the difference in the design and the difference in the calculated Q value are described.
Design Example 1: M = 90, N = 30, WCR = 32, TANC0 = −0.15, PPT = 0.800, PTN = 0.864
Design example 2: M = 90, N = 3, WCR = 32, TANC0 = −0.15, PPT = 0.800, PTN = 0.864

  As described above, Design Example 1 and Design Example 2 have the same values other than the number of conductors N of the reflector, and the value of N in Design Example 2 is set to be significantly smaller than the value of N in Design Example 1. ing. Here, considering the ratio between the number M of electrode finger pairs and the number N of reflector conductors, it can be considered that there is no reflector in the design example 2.

  When the Q value was calculated based on these conditions, the Q value in Design Example 1 was 6666, and the Q value in Design Example 2 was 5263. From this result, a change of about 1400 in Q value could be recognized between the SAW element piece of design example 1 and the SAW element piece of design example 2. This means that the reflection coefficient of the entire electrode including the IDT and the reflector can be increased or decreased by increasing or decreasing the number of conductors of the reflector. That is, by adjusting the PPT, the effective reflection coefficient of the IDT as a whole is lowered, and the SAW element piece whose Q value is lowered is added with a reflector to increase the reflection coefficient of the whole electrode and confine energy. It was confirmed that the Q value can be improved by achieving the effect. Based on the relationship as described above, the relationship PB <PR <PA exists between the electrode finger cycle lengths PA and PB and the reflector conductor cycle length PR, although it varies depending on the set conditions. It is considered desirable to hold.

  From the above, the bulk wave radiation in the IDT 14 is reduced by setting the electrode period length PPT, and the energy confinement effect is obtained by setting the number of conductor strips of the reflector 18, thereby increasing the film thickness of the electrode finger 22. Even when the reflection coefficient of the electrode finger 22 is increased, it is considered that the SAW element piece 10 having a high Q value can be obtained.

  Next, a surface acoustic wave device on which the SAW element piece 10 shown in the above embodiment is mounted will be described. FIG. 8 shows a specific example when the SAW element piece 10 shown in the above embodiment is used as a resonator.

  In FIG. 8, the SAW resonator 100 has a package body 102 made of ceramic or the like. The package body 102 is formed in a box shape having an open upper end, and the SAW element piece 10 is fixed to the bottom surface of the package body 102 with an adhesive or the like. The SAW element piece 10 is provided with connection pads 26 on both sides of the IDT 14. The connection pad 26 is connected to an electrode 106 provided on the package body 102 via a bonding wire 108 or the like. A lid 104 made of metal, glass, or the like is disposed in the opening of the package body 102 and hermetically sealed with a sealing agent (not shown). The SAW resonator 100 having such a configuration can maintain good temperature characteristics in a wide band, and can obtain a high Q value with little energy loss.

  Next, an electronic device in which the above-described surface acoustic wave device (SAW resonator 100) is mounted will be described using the cellular phone device shown in FIG. 9 as an example.

  In the mobile phone device 200, the audio signal from the transmitter is converted into an electric signal by the microphone 202, modulated by the signal switching unit 206 including a demodulator / codec, etc., frequency-converted, etc. by the transmission unit 208, and the antenna. It is transmitted to a base station (not shown) via 212.

On the other hand, a signal transmitted from the base station is received via the antenna 212, converted in frequency by the receiving unit 214, converted into an audio signal by the signal switching unit 206, and output from the speaker 204.
The operation of the cellular phone device 200 in which such signal control is performed is entirely controlled by a CPU (Central Processing Unit) 216. The CPU 216 also controls the operation of the input / output unit 218 such as a liquid crystal screen and a keyboard, the memory 220 that records a control program, a telephone directory, and the like, and the changeover switch 210 that controls transmission and reception of signals.

  In the mobile phone device 200 having the basic configuration as described above, the above-described SAW resonator 100 is particularly connected to the CPU 216 and serves as a basic clock of the CPU 216 and the like. When the surface acoustic wave device described above is used as a filter, it can be used as a filter in the transmission unit 208 and the reception unit 214, and can also serve as a local oscillator in the reception unit 214 as a resonator.

It is the schematic which shows the structure of the surface acoustic wave element concerning this invention. It is a figure explaining the cut angle of the crystal plate which concerns on an Example. It is a graph which shows the characteristic of the radiation conductance G of IDT14, and the characteristic of reflection coefficient (GAMMA). It is a graph which shows the characteristic of the radiation conductance G of IDT14, and the characteristic of reflection coefficient (GAMMA). It is a graph which shows the relationship between an electrode period length ratio and the frequency deviation of IDT. It is a graph which shows the relationship between the reflection coefficient of a reflector, and the frequency deviation of a stop band. It is a graph which shows the relationship between an electrode period length ratio and the maximum value of conductance. It is a figure which shows the example of the surface acoustic wave apparatus which concerns on this invention. It is a figure which shows the example of the electronic device which concerns on this invention.

Explanation of symbols

  10... Surface acoustic wave element piece (SAW element piece) 12... Piezoelectric substrate (quartz plate) 14... Interdigital electrode (IDT) 16 (16 a and 16 b). 18 (18a, 18b)... Reflector, 20... Feeding conductor (bus bar), 22... Electrode finger, 24.

Claims (6)

A surface acoustic wave element having interdigital electrodes with electrode fingers arranged on the plate surface of the piezoelectric substrate in a direction orthogonal to the traveling direction of the surface acoustic wave excited by the piezoelectric substrate,
A plurality of adjacent electrode fingers are set as one set, and sets having different period lengths forming the electrode fingers are alternately arranged,
A surface acoustic wave element piece characterized in that the interdigital electrode is sandwiched between reflectors having a plurality of conductor strips arranged in a grid pattern.   The surface acoustic wave element piece according to claim 1, wherein the electrode fingers forming each set are two electrode fingers forming pairs adjacent to each other of comb-shaped electrodes constituting interdigital electrodes.   The electrode finger formation cycle length of a set unit is composed of two sets of cycle lengths, and the cycle length ratio between sets is set in a range of 7:10 to 9:10. Surface acoustic wave element piece.   4. The interdigital electrode according to claim 1, wherein when the electrode fingers are formed with a predetermined period length, the line width of the electrode fingers and the interval between the intermittent portions are set to a constant ratio. The surface acoustic wave element piece according to any one of the above.   A surface acoustic wave device comprising the surface acoustic wave element according to claim 1.   An electronic apparatus comprising the surface acoustic wave device according to claim 5.

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