DESCRIPTION
`
`ELASTIC WAVE ELEMENT AND ELECTRONIC DEVICE
`
`USING THE SAME
`
`TECHNICAL FIELD
`
`The present invention relates to elastic wave devices and
`
`10
`
`electronic equipment using the elastic wave device.
`
`BACKGROUND ART
`
`15
`
`A conventional elastic wave device is described with reference to
`
`Figs. 9A and 93.
`
`Fig. 9A is a schematic sectional View of the-conventional elastic
`
`wave device. Fig. 9B is a graph indicating a range that an
`
`electromechanical coupling coefficient of Rayleigh wave becomes not
`
`20
`
`greater than a predetermined value when a cut angle of piezoelectric
`
`substrate is changed in the conventional elastic wave device.
`
`In Figs. 9A and 9B, conventional elastic wave device 1 includes
`
`piezoelectric substrate 2 made of lithium niobate, and IDT electrode 3
`disposed on piezoelectric substrate 2.
`In an area on piezoelectric
`
`25
`
`substrate 2 other than an area Where IDT electrode 3 is formed, first
`
`dielectric layer 6 made of silicon oxide film is formed in a thickness
`equivalent to IDT electrode 3.
`In addition, second dielectric layer 7 made
`
`of silicon oxide film covers IDT electrode 3 and first dielectric layer 6.
`
`
`
`ELASTIC WAVE ELEMENT AND ELECTRONIC DEVICE
`
`USING THE SAME
`
`TECHNICAL FIELD
`
`The present invention relates to elastic wave devices and
`
`10
`
`electronic equipment using the elastic wave device.
`
`BACKGROUND ART
`
`15
`
`A conventional elastic wave device is described with reference to
`
`Figs. 9A and 93.
`
`Fig. 9A is a schematic sectional View of the-conventional elastic
`
`wave device. Fig. 9B is a graph indicating a range that an
`
`electromechanical coupling coefficient of Rayleigh wave becomes not
`
`20
`
`greater than a predetermined value when a cut angle of piezoelectric
`
`substrate is changed in the conventional elastic wave device.
`
`In Figs. 9A and 9B, conventional elastic wave device 1 includes
`
`piezoelectric substrate 2 made of lithium niobate, and IDT electrode 3
`disposed on piezoelectric substrate 2.
`In an area on piezoelectric
`
`25
`
`substrate 2 other than an area Where IDT electrode 3 is formed, first
`
`dielectric layer 6 made of silicon oxide film is formed in a thickness
`equivalent to IDT electrode 3.
`In addition, second dielectric layer 7 made
`
`of silicon oxide film covers IDT electrode 3 and first dielectric layer 6.
`
`
`
`Normalized film thickness of second dielectric layer 7 is between
`
`0.15 A and 0.40 A, and (p in cut angles (0° i 5°, 6, (p) of piezoelectric
`
`substrate 2 is between 10° and 30°.
`
`In addition, if the film thickness of
`
`IDT electrode, for example, is 0.06 A, 6 and (9 fall in a range of hatched
`
`area in Fig. QB.
`
`This enables to reduce the electromechanical coupling coefficient of
`
`Rayleigh wave, which is not a major wave, so as to suppress spurious due
`
`to Rayleigh wave. Conventional elastic wave device 1 as configured
`
`above sets the cut angle of piezoelectric substrate 2, film thickness of IDT
`
`10
`
`electrode 3, and film thickness of second dielectric layer 7 so as to reduce
`
`the electromechanical coupling coefficient of Rayleigh wave. This
`
`suppresses a spurious response caused by the Rayleigh wave.
`
`However, if this conventional elastic wave device 1 is a boundary
`wave device that traps major waves inside the device, the film thickness
`
`15
`
`of IDT electrode 3, film thickness of dielectric layer, and so on often
`
`become out of conditions that can suppress Stoneley waves, due to
`
`manufacturing variations. This manufacturing variations cause
`
`spurious responses by Stoneley waves, resulting in deteriorating device
`
`characteristics.
`
`[Citation List]
`
`[Patent Literature]
`
`[PTL 1] Japanese Patent Unexamined Publication No. 2007'251710
`
`20
`
`25
`
`
`
`SUMMARY OF THE INVENTION
`
`The present invention offers an elastic wave device that
`
`suppresses deterioration of device characteristics even if there are
`
`manufacturing variations.
`
`The elastic wave device of the present invention includes a
`
`piezoelectric substrate, an IDT electrode disposed on the piezoelectric
`substrate, a first dielectric layer disposed on the piezoelectric substrate
`
`such that it covers the IDT electrode, and a second dielectric layer
`
`10
`
`disposed over the first electric layer. Transverse waves propagate faster
`
`on the second dielectric layer than that on the first dielectric layer.
`
`When the film thickness of second dielectric layer is more than 0.8 times
`
`as large as wavelength A of major waves excited by IDT electrode, a cut
`
`angle of piezoelectric substrate in indication of Euler angles (¢, 6, (p) is set
`
`15
`
`to 475 960°, B¢O°, andrpgéO9.
`
`By shifting cut angle ¢ of piezoelectric substrate from 0° in the
`
`elastic wave device of the present invention, a power flow angle of SH
`
`wave, which is a major wave, becomes not greater than a predetermined
`
`value, and a power flow angle of Stoneley wave becomes not less than a
`
`20
`
`predetermined value.
`
`In other words, in a boundary wave device in
`
`which manufacturing variations often occur, deterioration of device
`
`characteristics can be suppressed to a permissible level even if the film
`
`thickness of IDT electrode, film thickness of dielectric layer, and so on
`
`become out of conditions for suppressing Stoneley waves and the power
`
`25
`
`flow angle of Stoneley waves become slightly smaller.
`
`
`
`BRIEF DESCRIPTION OF. DRAWINGS
`
`Fig. 1 is a schematic sectional View of an elastic wave device in
`
`accordance with a first exemplary embodiment of the present invention.
`
`Fig. 2 illustrates characteristics of the elastic wave device in
`
`accordance with the first exemplary embodiment of the present invention.
`
`Fig. 3 illustrates characteristics of the elastic wave device in
`
`10
`
`accordance with the first exemplary embodiment of the present invention.
`
`Fig. 4 illustrates characteristics of the elastic wave device in
`
`accordance with the first exemplary embodiment of the present invention.
`
`Fig. 5 illustrates characteristics of the elastic wave device in
`
`accordance with the first exemplary embodiment of the present invention.
`
`15
`
`Fig. 6 illustrates characteristics of the elastic wave device in
`
`accordance with the first exemplary embodiment of the present invention.
`
`Fig. 7 illustrates characteristics of the elastic wave device in
`
`accordance with the first exemplary embodiment of the present invention.
`
`Fig. 8 illustrates characteristics of the elastic wave device in
`
`20
`
`accordance with the first exemplary embodiment of the present invention.
`
`Fig. 9A is a schematic sectional view of a conventional elastic wave
`
`device.
`
`Fig. 9B illustrates a range of electromechanical coupling coefficient
`
`of Rayleigh wave in the conventional elastic wave device.
`
`25
`
`k3)
`
`
`
`DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
`
`(FIRST EXEMPLARY EMBODIMENT)
`
`An elastic wave device in the first exemplary embodiment is
`
`described below with reference to drawings.
`
`Fig. 1 is a schematic sectional View of elastic wave device 8 in the
`first exemplary embodiment of the present invention.
`In Fig. ’1, elastic
`
`wave device 8 includes piezoelectric substrate 9, IDT (Inter-Digital
`
`10
`
`Transducer) electrode 10 disposed on piezoelectric substrate 9, first
`
`dielectric layer 11 disposed on piezoelectric substrate 9 such that first
`
`dielectric layer 11 covers IDT electrode 10, and second dielectric layer 12
`
`provided over first dielectric layer 11.
`
`Piezoelectric substrate 9 is formed of, for example, lithium niobate,
`
`15
`
`lithium tantalite, or potassium niobate. A cut angle of this piezoelectric
`
`substrate 9 in indication of Euler angles is ¢ gé 0°, 9 7E 0°, and (pi 0°. For
`
`example, the cut angle of piezoelectric substrate 9 is 13" < ¢ < 5.5", '70°
`
`< 6 < ‘60°, and —3.4° < (p < 0°.
`
`IDT electrode 10 is, for example, single metal of aluminum, copper,
`
`20
`
`silver, gold, titanium, tungsten, Molybdenum , platinum, or chromium, or
`
`an alloy mainly consists of these metals.
`First dielectric layer 11 is, for example, made of silicon oxide.
`
`HoweVer, first dielectric layer 11 may be any medium that has frequency-
`
`temperature characteristic opposite to that of piezoelectric substrate 9.
`
`25
`
`This improves the frequency-temperature characteristic.
`
`
`
`Second dielectric layer 12 is formed of a medium that propagates
`
`transverse waves faster than the speed of transverse waves propagating
`
`on first dielectric layer 11. For example, diamond, silicone, silicone
`
`nitride, aluminum nitride, or aluminum oxide is used. The film
`
`thickness of this second dielectric layer 12 is not less than 0.8 times as
`
`large as wavelength A of SH wave, which is a major wave. This enables
`
`to trap the major wave inside elastic wave device 8. To almost
`
`completely trap the major wave inside elastic wave device 8, the film
`
`thickness of second dielectric layer 12 is preferably not less than
`
`10
`
`wavelength A of SH wave that is the major wave.
`
`In the above structure, a power flow angle of SH wave that is the
`
`major wave becomes not greater than a predetermined value, and a power
`
`flow angle of Stoneley wave becomes not less than the predetermined
`
`value by shifting cut angle ¢ of piezoelectric substrate 9 from 0°. The
`
`15
`
`power flow angle is an angle formed by a direction of propagating phase
`
`velocity and a direction of group velocity when waves are excited by IDT
`
`electrode 10.
`
`Accordingly, in a boundary wave device in which manufacturing
`
`variations frequently occur, deterioration of device characteristics can be
`
`20
`
`suppressed to a permissible level even if the film thickness of IDT
`
`electrode 10, the film thickness of dielectric layer, and so on are out of
`
`conditions that can suppress Stoneley waves, and the power flow angle of
`
`Stoneley waves becomes slightly smaller than the predetermined value.
`
`This is detailed below.
`
`
`
`Fig. 2 illustrates characteristics of the elastic wave device in the
`
`first exemplary embodiment of the present invention.
`
`In Fig. 2, a
`
`vertical axis indicates PFA (power flow angle) of SH wave that is major
`
`wave (Unit: deg) or PFA (power flow angle) of Stoneley wave that is
`
`undesired wave (Unit: deg). Fig. 2 shows cases when the cut angle of
`
`piezoelectric substrate 9 is 0 = '65° and 45 = 0°, 1°, 2°, 3°, 4°, and 5°.
`
`In elastic wave device 8, lithium niobate is used as piezoelectric
`
`substrate 9, and copper With normalized film thickness of 0.09}; Ox is
`
`wavelength of SH wave) as IDT electrode 10. Silicon oxide with
`
`10
`
`normalized film thickness of 0.2L is used as first dielectric layer 11, and
`
`silicon nitride with normalized film thickness A is used as second
`
`dielectric layer 12.
`
`Focusing on SH wave that is major wave in Fig. 2, it can be found
`
`that (p that sets 0° to PFA of SH wave that is major wave changes from 0°
`
`15
`
`by changing ¢. Accordingly, by using (p that sets 0° to PFA of SH wave
`
`that is major wave, deterioration of Q value of SH wave that is major
`
`wave can be suppressed. Deterioration of Q value can thus be
`
`suppressed when an absolute value of power flow angle of SH wave
`
`excited by IDT electrode 10 becomes less than 0.3°.
`
`20
`
`Focusing on Stoneley wave that is undesired wave, it can be found
`
`that PFA of Stoneley wave that is undesired wave also becomes 0° if (p
`
`that sets 0° to PFA of SH wave that is major wave is adopted in the case
`
`that cut angle ¢ of piezoelectric substrate 9 is 0°. Therefore, elastic
`
`wave device 8 in the first exemplary embodiment can shift PFA of
`
`25
`
`Stoneley wave that is undesired wave from 0° by setting a value other
`
`
`
`than 0° to cut angle ¢ of piezoelectric substrate 9 if (9 that sets 0° to PFA
`
`of SH wave that is major wave is adopted.
`
`Based on the above results, a Q value of Stoneley wave that is
`
`undesired response can be reduced by changing cut angle ¢ of
`
`piezoelectric substrate 9 from 0°. This enables selective suppression of
`
`spurious response.
`
`Next is described a range of cut angles of piezoelectric substrate 9
`
`when an absolute value of power flow angle of SH wave excited by IDT
`
`electrode 10 becomes less than 0.3° and an absolute value of power flow
`
`10
`
`angle of Stoneley wave excited by IDT electrode 10 becomes not less than
`
`O.3° in the above elastic wave device 8, with reference to Figs. 3 to 6.
`
`Figs. 3 to 6 are charts illustrating characteristics of elastic wave
`
`device in the first exemplary embodiment of the present invention. Figs.
`
`3 to 6 show ranges of cut angles of piezoelectric substrate 9 when the
`
`15
`
`absolute value of power flow angle of SH wave is less than 0.3° and the
`
`absolute value of power flow angle of Stoneley wave is not-less than 0.3°.
`
`In these charts, ranges of ¢ and (p are hatched when 8 is “75° in Fig. 3, 9
`
`is '70° in Fig. 4, 9 is '65° in Fig. 5, and 9 is '60° in Fig. 6, provided that
`
`the cut angle of piezoelectric substrate is indicated by Euler angles (¢, 0,
`
`20
`
`(p).
`
`Here, lithium niobate is used as piezoelectric substrate 9, copper
`
`with normalized film thickness of 0.09 A (A is wavelength of SH wave) is
`
`used as IDT electrode 10, silicon oxide with normalized film thickness of
`
`0.2A is used as first dielectric layer 11, and silicon nitride with normalized
`
`25
`
`film thickness A is used as second dielectric layer 12.
`
`
`
`As shown in Figs. 3 to 6, the absolute value of power flow angle of
`
`SH wave excited by IDT electrode 10 becomes less than 0.3 ° and the
`
`absolute value of power flow angle of Stoneley wave excited by IDT
`
`electrode 10 becomes not less than 0.3 ° when the cut angle of
`
`piezoelectric substrate 9 satisfies the following conditions.
`
`In other words, the cut angle of piezoelectric substrate 9 of elastic
`
`wave device 8 satisfies the following conditions.
`
`i) When —77.5° s 8 < -72.5°,
`
`'0.5° S (15 < 0.5° and 22° S (p < '1.4°
`
`or
`
`0.5° S ¢ < 1.5° and '2.4° S (p < 'O.8°
`
`or
`
`1.5° 3 ¢ < 2.5° and -2.6° s (p < -0.2°
`
`or
`
`2.5° S ¢ < 3.5° and ~2.8° S (p < 03°
`
`or
`
`3.5° S (I5 < 4.5° and -3.1° S (p < 0.8°
`
`or
`
`4.5° 5 ¢ < 5.5° and -3.3° S<p < 113°
`
`20
`
`ii) When —72.5° S 6 < '67.5°,
`
`'O.5° S (15 < 0.5° and 25° S (p < '1.7°
`
`or
`
`0.5° S ¢ < 1.5° and '2.6° S (p < '0.9°
`
`or
`
`25
`
`1.5° S {15 < 2.5° and '2.7° S (p < '0.1°
`
`
`
`10
`
`or
`
`2.5° 5 ¢ < 3.5° and -2.7° S (p < 0.7°
`
`or
`
`3.5° 5 ¢ < 4.5° and -2.9° S (p < 13°
`
`or
`
`4.5° S {15 < 5.5° and '3° 5 (p < 2°
`
`iii) When —67.5° S 9 < '62.5°,
`
`'O.5° 5 ¢ < 0.5° and '3.2° S (p < 22°
`
`or
`
`10
`
`0.5° 5 ¢ < 1.5° and 3° 5 (p < —0.9°
`
`or
`
`1.5° 5 915 < 2.5° and '2.7° S (p < 0.4°
`
`or
`
`2.5° 5 ¢ < 3.5° and 25° 5 (p < 1.5°
`
`15
`
`or
`
`3.5° 5 ¢ < 4.5° and -2.4° s (p < 26°
`
`or
`
`4.5° 5 ¢ < 5.5° and —2.4° 5 cp < 3.3°
`
`iv) When "625° 5 9 < '57.5°,
`
`20
`
`'O.5° 5 ¢ < 0.5° and "52° 5 (I) < '4.1°
`
`or
`
`0.5° 5 (15 < 1.5° and -4° _<_ (p < ‘0.8°
`
`or
`
`1.5° 5 ¢ < 2.5° and 28° 5 (p < 2.1°
`
`25
`
`OI'
`
`
`
`ll
`
`2.5° 5 ¢ < 3.5° and -1.8° S (p < 4.1°
`
`pr
`
`3.5° 5 {15 < 4.5° and '1.1 S (p < 5.5°
`
`or
`
`4.5° 5 ¢ < 5.5° and '0.9° S (p < 6.2°
`
`When the above conditions are satisfied, the power flow angle of
`
`SH wave that is major wave becomes less than 0.3°, and the absolute
`
`value of power flow angle of Stoneley wave becomes not less than 0.3°.
`
`Accordingly, propagation losses of SH wave can be reduced, and also
`
`10
`
`spurious response of Stoneley wave can be suppressed.
`
`Fig. 7 shows characteristics of the elastic wave device in the first
`
`exemplary embodiment of the present invention. More specifically, it
`
`shows a range of cut angles of piezoelectric substrate 9 that makes the
`
`absolute value of power flow angle of SH wave less than 03° and the
`
`15
`
`absolute value of power flow angle of Stoneley wave not less than 03°
`
`when the normalized film thickness of IDT electrode 10 is 0.08A (A is
`
`wavelength of SH waves) or 0.12k.
`
`.
`
`In Fig. 7, an area between two dotted lines connecting triangles
`
`shews the case when the film thickness of IDT electrode 10 is 0.08)» An
`
`20
`
`area between two dotted lines connecting circles shows the case when the
`
`film thickness of IDT electrode 10 is 0.12)» Elastic wave device 8 shown
`
`in Fig. 7 has the structure same as elastic wave device 8 shown in Fig. 5
`
`except for the film thickness of IDT electrode 10.
`
`Fig. 8 shows characteristics of the elastic wave device in the first
`
`25
`
`exemplary embodiment of the present invention. More specifically, it
`
`'
`
`
`
`12
`
`shows a range of cut angles of piezoelectric substrate 9 that makes the
`
`absolute value of power flow angle of SH wave less than 0.3° and the
`
`absolute value of power flow angle of Stoneley wave not less than 0.3°
`
`when the normalized film thickness of first dielectric layer 11 is 0.1}; (A is
`
`wavelength of SH wave) or 0.4K.
`
`In Fig. 8, an area between two dotted lines connecting triangles
`
`shows the case when the film thickness of first dielectric layer 11 is 0.4K.
`
`An area between two dotted lines connecting circles shows the case when
`
`the film thickness of first dielectric layer 1 1 is 0.1K. Elastic wave device
`
`10
`
`8 shown in Fig. 8 has the structure same as elastic wave device 8 shown
`
`in Fig. 5 except for the film thickness of first dielectric layer 11.
`
`It is apparent from Figs. 7 and 8 that the ranges of cut angles of
`
`piezoelectric substrate 9 that make the absolute value of power flow angle
`
`of SH wave less than 0.3° and the absolute value of power flow angle of
`
`15
`
`Stoneley wave not less than 0.3° also depend on the film thickness and
`
`density of IDT electrode 10 and the film thickness of first dielectric layer
`
`11.
`
`Correction functions F1 and F1 for cut angle (9 of piezoelectric
`
`substrate 9 that satisfies the above conditions when the film thickness
`
`20
`
`and density of IDT electrode 10 and the film thickness of first dielectric
`
`layer 11 change are expressed by Equation 1 and Equation 2, respectively.
`
`F1 is the correction function for the upper limit of (p that satisfies
`
`the above conditions relative to¢. F2 is the correction function for lower
`
`limit of (p that satisfies the above conditions relative to ¢. The elastic
`
`25
`
`wave device before correction is the same as above elastic wave device 8.
`
`
`
`13
`
`In other words, elastic wave device 8 includes first dielectric layer 11
`
`made of silicon oxide With the normalized film thickness of 0.2K and IDT
`
`electrode 10 made of copper with the normalized film thickness of 0.09)»
`
`[Equation 1]
`
`5
`
`10
`
`%—0.2
`62—17—009
`F1: mg1(¢)+ mmw)
`
`[Equation 2]
`fl—OZ
`Elfi-—0.09
`F2=Wg2<¢>+gmhzw
`
`Whereas, h is the film thickness of IDT electrode 10, a is the ratio
`
`of density of IDT electrode 10 to density of copper, and H is the film
`
`thickness of first dielectric layer 11.
`
`The above gl ({1}), g2 (¢), h1 (¢), and h2 ((15) are expressed by
`
`15
`
`Equation 3, Equation 4, Equation 5, and Equation 6 below.
`
`[Equation 3]
`g1(¢) = 0.0352152 — 0.0852¢ — 0.3795
`
`[Equation 4]
`g2(¢) = 0.0589052 — 0.4089¢ + 0.7821
`
`2 0
`
`[Equation 5]
`h1(¢) = 0.0161¢2 — 0.1175¢ + 0.6964
`
`[Equation 6]
`h2(¢) = —0.0339¢2 + 0.5496¢ —1.3464
`
`
`
`14
`
`Here, the above g1 (¢) and g2 (40 are correction functions that
`
`show dependency on the film thickness and density of IDT electrode 10.
`
`The above h1 (¢) and h2 (¢) are correction functions that show
`
`dependency on the film thickness of first dielectric layer 1 1.
`
`In other words, when correction functions F1 and F2 are expressed
`
`using Equation 1 and Equation 2, the cut angle of piezoelectric substrate
`
`9 in elastic wave device 8 satisfies the following conditions.
`
`i) When '77.5° S G < -72.5°,
`
`"0.5° 5 ¢ < 0.5° and ”22° + F2 5 (p < '1.4° + F1
`
`or
`
`0.5° 5 ¢ < 1.5° and "24° + F2 5 (p < 'O.8° + F1
`
`or
`
`1.5° 5 ¢ < 2.5° and 26° + F2 S (p < 02° + F1
`
`or
`
`25° 5 (15 < 3.5° and '2.8° + F2 5 (p < 0.3° + F1
`
`01'
`
`3.5° _<_ ¢ < 4.5° and '3.1° + F2 S (p < 0.8° + F1
`
`or
`
`45° 5 ¢ < 5.5° and '3.3° + F2 5 (p < 1.3° + F1
`
`20
`
`ii) When -72.5° 5 e < -67.5°,
`
`'0.5° S (I) < 0.5° and '2.5° + F2 S (p < '1.7° + F1
`
`or
`
`0.5° 5 ¢ < 1.5° and '2.6° + F2 E (p < 'O.9° + F1
`
`or
`
`25
`
`1.5° 5 ¢ < 2.5° and —2.7° + F2 5 (p < -0.1° + F1
`
`
`
`15
`
`01'
`
`2.5° 5 ¢ < 3.5° and 27° + F2 5 (p < 0.7° + F1
`
`or
`
`3.5° s (/5 < 4.5° and -2.9° + F2 3 (p < 13° + F1
`
`01‘
`
`4.5°: ¢ <5.5°and-3°+F25cp<2°+F1
`
`iii) When —67.5° s e < -62.5°,
`
`-O.5° 5 (15 < 0.5° and 32° + F2 S (p < '2.2° + F1
`
`01‘
`
`‘
`
`10
`
`0.5° 5 ¢ < 1.5° and -3° + F2 5 (p < -0.9° + F1
`
`01'
`
`1.5° 5 ¢ < 2.5° and -2.7° + F2 5 (p < 0.4° + F1
`
`01‘
`
`2.5° 5 ¢ < 3.5° and -2.5° + F2 5 (p < 1.5° + F1
`
`15
`
`01'
`
`3.5° 5 (15 < 4.5° and '2.4° + F2 5 (p < 2.6° + F1
`
`01'
`
`4.5° 5 ¢ < 5.5° and 24° + F2 5 (p < 33" + F1
`
`iv) When —62.5° s e < -57.5°,
`
`20
`
`-0.5° 5 ¢ < 0.5° and -5.2° + F2 5 (p < -4.1° + F1
`
`01'
`
`0.5° 5 ¢ < 1.5° and ~4° + F2 5 (p < -0.8° + F1
`
`01‘
`
`1.5° S ¢ < 2.5° and -2.8° +F2 S (p < 2.1° + F1
`
`25
`
`01'
`
`
`
`I6
`
`2.5° 5 ¢ < 3.5° and -1.8° + F2 3 (p < 4.1° + F1
`
`or
`
`_
`
`35° 5 ¢ < 4.5° and '1.1° + F2 5 (p < 5.5° + F1
`
`or
`
`I
`
`4.5° S (15 < 5.5° and '0.9° + F2 S (p < 62° + F1
`
`When the above conditions are satisfied, the absolute value of
`
`power flow angle of SH wave that is major wave becomes less than 03°,
`
`and the absolute value of power flow angle of Stoneley wave becomes not
`
`less than 03°. Accordingly, propagation losses of SH waves can be
`
`10
`
`reduced, and also spurious response of Stoneley waves can be suppressed.
`
`Elastic wave device 8 in the first exemplary embodiment may be
`
`applied to a resonator (not illustrated), or a filter (not illustrated) such as
`
`a ladder filter and DMS filter.
`
`In addition, elastic wave device 8 may be
`
`applied to electronic equipment including this filter, a semiconductor
`
`15
`
`integrated circuit device (not illustrated) connected to the filter, and a
`reproducing unit connected to the semiconductor integrated circuit device
`
`(not illustrated).
`
`This improves the communications quality of a
`
`resonator, filter, and electronic equipment.
`
`20
`
`25
`
`INDUSTRIAL APPLICABILITY
`
`The elastic wave device of the present invention suppresses
`
`deterioration of device characteristics, and is applicable to electronic
`
`equipment such as mobile phones.
`
`
`
`l7
`
`REFERENCE MARKS IN THE DRAWINGS
`
`8
`
`9
`
`10
`
`11
`
`12
`
`Elastic wave device
`
`Piezoelectric substrate
`
`IDT electrode
`
`First dielectric layer
`
`Second dielectric layer
`
`
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