JPH0483235A - Surface acoustic wave element - Google Patents

Abstract

PURPOSE:To obtain the surface acoustic wave(SAW) element which is easily manufacture and small in size while making the frequency high by making the phase speeds of SAWs faster in SAW generation areas than in an SAW propagation area. CONSTITUTION:The element consists of a piezoelectric layer 3b and a layer 1b having no piezoelectricity and has the SAW generation areas 7c and 7b and SAW propagation area 8b, and at least one of the piezoelectric layer 3b and nonpiezoelectric layer 1b differs in film thickness between the SAW generation areas 7c and 7d and SAW propagation area 8b. Then the phase speeds v1 and v2 of the SAWs in the SAW generation areas 7c and 7d are made faster than the phase speeds v11 and v22 of the SAWs in the SAW propagation area 8b. Consequently, the SAW element is miniaturized.

Description

[Detailed Description of the Invention] [Summary] Regarding a surface acoustic wave element made of a piezoelectric material and a non-piezoelectric material such as a semiconductor, the present invention relates to a surface acoustic wave element that is small and easy to manufacture even at a high operating frequency. For the purpose of realizing an element, it consists of a piezoelectric layer and a non-piezoelectric layer, and has a surface acoustic wave generation region and a surface acoustic wave propagation region, and the film thickness of the piezoelectric layer. The thickness of at least one layer is different between the surface acoustic wave generation region and the surface acoustic wave propagation region, and the phase velocity of the surface acoustic wave in the surface acoustic wave generation region is , is thicker than the phase velocity of the surface acoustic wave in the surface acoustic wave propagation region.

[Industrial application field]

The present invention relates to a surface acoustic wave device made of a piezoelectric body and a non-piezoelectric material such as a semiconductor, and particularly to a monolithic surface acoustic wave device.

(1) Spread spectrum communication method and convolver wireless communication technology have come to be used in a wide range of social life, and small zone communication used for FA, OA, HA, mobile devices, etc. has become an important part of new product development. It is attracting attention when doing this.

However, in many cases, the quality of the communication channel is poor, and line management is easy, so interference, eavesdropping, interference, etc. are likely to occur.

Spread spectrum communication is attracting the most attention as a new communication method that overcomes these problems.

In the spread spectrum communication method, the transmitted data is modulated with a carrier wave and a predetermined code (pseudo-noise code: PN code) to spread the spectrum and form the transmitted wave, so only those who know the PN code in advance can receive the radio wave. , it is possible to obtain phase synchronization by making full use of the PN code and remove the carrier wave to obtain data.

Therefore, it has the following excellent features:

■Only those who know the ρN code can obtain the information (it is confidential).

■The power density per unit frequency width is small and the existence of the signal is unknown (there is secrecy).

■Communication is possible even with weak radio waves.

■Strong against interference.

■Does not interfere with other spread spectrum communications.

■Strong for communication channels with poor conditions.

■It is possible to use the same frequency band at the same time.

■Random access with multiple access is possible.

■Overload communication is possible.

On the other hand, a convolver used in a spread spectrum communication receiver is an indispensable element for performing part of synchronization acquisition and signal reconstruction processing. In other words, in order to obtain baseband information, the PN code of the received signal is compared with the PN code owned by the receiver (compollution), and at the same time as synchronization acquisition, a part of the baseband signal regeneration is performed. .

(2) Overview of Convolver and Surface Acoustic Wave Element Convolvers can be roughly divided into those using digital circuits, elements using nonlinearity of physical properties related to surface acoustic waves, and elements using nonlinearity of semiconductor physical properties.

1) Convolver using a digital circuit A convolver using a digital circuit has the disadvantage that it uses a large amount of ICs, etc., has a complicated configuration, is large and heavy, and consumes a lot of power.

In addition, the operating frequency is determined by the IC used, and because high frequency clocks cannot be created, currently 100%
It cannot be used for spread spectrum communication using frequencies higher than MHz.

2) Convolvers that use nonlinearity of physical properties related to surface acoustic waves Convolvers that use nonlinearity of physical properties related to surface acoustic waves are those that use nonlinearity due to second-order distortion accompanying the propagation of surface acoustic waves, and those that use nonlinearity due to second-order distortion that accompanies the propagation of surface acoustic waves. It can be divided into those that use the nonlinearity of dielectric constant, elastic constant, and piezoelectric constant.

However, both require a large energy density on the surface of the propagation medium, and therefore necessarily require a large input power, which goes against the advantage of spread spectrum communication in that it is resistant to interference and noise even with weak radio waves.

3) Convolver using nonlinearity of semiconductor physical properties Convolver using nonlinearity of semiconductor physical properties (semiconductor convolver)
The method uses the nonlinear response of the space charge in the semiconductor interface depletion layer, and is efficient because it uses varactor-diode-like capacitance changes on the semiconductor surface.

Therefore, semiconductor convolvers are surface acoustic wave elements that are currently attracting attention, and there is a demand for convolvers that are small, easy to manufacture, and usable at high frequencies.

(3) Optical communication technology and surface acoustic wave devices In the field of optical communication systems, integrated circuits that utilize optical surface waves and surface acoustic waves, so-called optical ICs, are attracting attention. There is a need for (optical) surface acoustic wave devices that operate efficiently.

[Conventional technology]

FIG. 6 is a diagram illustrating a semiconductor convolver, in which (a) is a cross-sectional view of the semiconductor convolver, and (b) is a plan view.

Semiconductor convolvers are basically made of zinc oxide Z, which is a piezoelectric material.
The n0O layer 3a and the silicon Si0 layer 1a, which is a semiconductor,
Two input IDTs (interdigital transdus
ser) 4a and 4b to excite surface acoustic waves. Incidentally, the input IDTs 4a and 4b are formed using lithography technology.

Then, excited by the input IDTs 4a and 4b, Z
The surface acoustic wave 20 of the received signal and the surface acoustic wave 21 of the reference PN code propagating in opposite directions in the n0 layer 3a radiate an electric field, and the radiated spatial electric field distribution spreads through the Si layer on the side in contact with the SiO□ layer 2a. It is applied to the depletion layer 22 near the surface of 18 to perform convolution.

Comporous silane results are shown on Zn0 layer 3a and Si layer 1a.
It is detected by the gate electrodes 5a and 5b provided above, and the output terminal 6
Output to a and 6b.

Incidentally, the regions where the input IDTs 4a and 4b are present and which excite surface acoustic waves are called surface acoustic wave generation regions 7a and 7b, and the region where surface acoustic waves propagate in opposite directions and interfere with each other is called a surface acoustic wave propagation region 8a. It is called. Gate electrodes 5a and 5b are provided in surface acoustic wave propagation region 8a.

[Problem to be solved by the invention]

In a semiconductor convolver, the phase velocity is 5 as a surface acoustic wave.
000m/s or more Sezawa waves are used, and the delay time is 1
When a 0 μs propagation path is configured, its length is 50 mm or more.

Therefore, the element has a large external shape, which hinders miniaturization of communication devices.

On the other hand, - input IDT 4a that generates surface acoustic waves for boat fishing;
, 4b is approximately λ/4, where λ is the wavelength. Therefore, when the frequency is l GHz, the wavelength λ is 5 μm
Therefore, the width of the input IDTs 4a and 4b is 1.25 μm.

By the way, in order to make the operating frequency of a semiconductor convolver using the same material 2G)lz, the wavelength λ must be 2.5pm.
Therefore, the width of the input IDTs 4a and 4b is approximately 0.63 μm. Therefore, it cannot be manufactured using current process technology using photolithography technology.

The technical problem of the present invention is to solve the above-mentioned problems with conventional surface acoustic wave devices, to realize a surface acoustic wave device that is small and easy to manufacture even at high operating frequencies, and is inexpensive. The goal is to enable high-quality communication.

This is a surface acoustic wave element whose phase velocity is larger than Vll+V2□.

[Means to solve the problem] FIG. 1 is a sectional view illustrating the basic principle of the present invention.

The present invention increases the phase velocity Vl+ν2 of the surface acoustic wave in the surface acoustic wave generation regions 7c and 7d, and increases the phase velocity V11, ν2 of the surface acoustic wave in the surface acoustic wave propagation region 8b.
The characteristic is that the □ is made small ().

(1) A surface acoustic wave element with a different thickness of the propagation medium, consisting of a piezoelectric layer 3b and a non-piezoelectric layer 1b, and
Surface acoustic wave generation regions 7c and 7d and surface acoustic wave propagation region 8
b, the thickness of the layer 3b having piezoelectricity, the thickness of the layer 1b not having piezoelectricity, or the layer 3 having piezoelectricity.
The thicknesses of both the layer 1b and the non-piezoelectric layer 1b are different between the surface acoustic wave generation regions 7c and 7d and the surface acoustic wave propagation region 8b, and the phase of the surface acoustic wave in the surface acoustic wave generation regions 7c and 7d is different. The velocity 2, the electric current 2, the surface acoustic wave propagation region 8b
Surface acoustic wave (2) Surface acoustic wave element with different types of propagation medium Layer 3b with piezoelectricity and layer 1 without piezoelectricity
a layer 3 having piezoelectric properties, comprising surface acoustic wave generation regions 7c and 7d and a surface acoustic wave propagation region 8b;
The type b, the type of the layer 1b that does not have piezoelectricity, or the type of both the layer 3b that has piezoelectricity and the layer 1b that does not have piezoelectricity, the surface acoustic wave generation regions 7c and 7d and the surface acoustic wave propagation region. 8b, the surface acoustic wave generation region 7c
, 7d, the phase velocity of the surface acoustic wave ν1. This is a surface acoustic wave element in which v2 is larger than the phase velocity νIl+V22 of the surface acoustic wave in the surface acoustic wave propagation mode 8b.

(3) Surface acoustic wave element with different propagation mode It consists of a piezoelectric layer 3b and a non-piezoelectric layer 1b, and includes surface acoustic wave generation regions 7c and 7d and a surface acoustic wave propagation region 8b. Therefore, the surface acoustic wave propagation mode in the surface acoustic wave propagation region 8b is different from the surface acoustic wave propagation mode in the surface acoustic wave generation regions 7c and 7d, and the phase velocity of the surface acoustic wave in the surface acoustic wave generation regions 7c and 7d is different. Vl+V
This is a surface acoustic wave element in which Z is larger than the phase velocity Vll+V22 of the surface acoustic wave in the surface acoustic wave propagation region 8b.

(4) Surface acoustic wave device with a different direction of phase velocity (1)
), the boundary between the surface acoustic wave generation regions 7c and 7d and the surface acoustic wave propagation region 8b with different film thicknesses, the direction of phase velocity before the surface acoustic wave passes through it, and the direction of the phase velocity after passing through the boundary between the surface acoustic wave generation regions 7c and 7d and the surface acoustic wave propagation region 8b. This is a surface acoustic wave element configured so that the directions of the phase velocities are different from each other. Further, in the surface acoustic wave element described in (2) above, the phase of the surface acoustic wave before it passes through the boundary between different types of layers, that is, the boundary between the surface acoustic wave generation regions 7c and 7d and the surface acoustic wave propagation region 8b. This is a surface acoustic wave element configured such that the direction of velocity is different from the direction of phase velocity after passing.

[Operation] Input rDT 4c,
The phase velocity Vl+V2+VII+VZ at which the surface acoustic wave propagates is changed by changing the surface acoustic wave generation regions 7c and 7d in which the surface acoustic waves are excited by 4d and the surface acoustic wave propagation region 8b in which the surface acoustic waves propagate. changes.

Then, the phase velocity of the surface acoustic waves in the surface acoustic wave generation regions 7c and 7d is vl+v! and surface acoustic wave propagation region 8
Phase velocity of surface acoustic wave at b 'l I + VZ□
The relationship between them is expressed by the following equations (1) and (2).

ν direct>v, 1 ----------(1) V2>νZ 2 ----------(2) Therefore, the wavelength λ1 of the surface acoustic wave in the surface acoustic wave generation regions 7c and 1d. λ2, and the wavelength λ11 of the surface acoustic wave in the surface acoustic wave propagation region 8b. The relationship with λ2□ is expressed by the following formula (
3) (4) becomes.

λ Leisure〉　λth－－－－－(3) λ2〉　λt’l　−1111(4) By the way, the input rDT 4c generates surface acoustic waves.

The widths w and w2 of 4d are made to have the relationship shown in the following equations (5) and (6) for - boat fishing.

W1ζλ, /4 ---(5) Wz ′=, λ2 /4 ---(6) Therefore, the width W,, W of the input rDT 4c4d that excites the surface acoustic wave
g can be made to a size that is easy to manufacture.

Further, the length of the surface acoustic wave propagation region 8b is given by the following equation (7), where τ is the delay time of the surface acoustic wave in the surface acoustic wave propagation region 8b, and f is the operating frequency of the surface acoustic wave element. It will be done.

L=fτλ” --- (7) Therefore, λ13λI+=λ2□.

Therefore, the length can be shortened while maintaining f and τ.

Equations (5) and (6) above (from force, input TDT 4c, 4
A surface acoustic wave element with a small external shape can be obtained while d remains at a size that is easy to manufacture.

By the way, when surface acoustic waves propagate across boundaries with different film thicknesses or different types of films, the surface acoustic waves are reflected at the boundaries, and the reflected waves cause interference, deteriorating the characteristics of the surface acoustic wave element. do.

Therefore, by changing the direction of the phase velocity before the surface acoustic wave passes through the boundary and the direction of the phase velocity after passing through the boundary, interference between the reflected wave at the boundary and the reflected wave is suppressed.

[Examples] Next, examples will explain how the present invention can be practically embodied.

(1) Example-1 FIG. 2 is a diagram explaining Example-1, in which (a) is a cross-sectional view of a semiconductor convolver, and (b) is a plan view.

Example 1 uses a surface-oxidized Si/Si'' substrate 1d/Ic as a layer that does not have piezoelectricity, and a layer on which ZnO 3c is formed by RF sputtering or RF magnetron sputtering as a layer that has piezoelectricity. The side surfaces of the gate electrodes 5c and 5d on the surface acoustic wave input side are inclined by several degrees from the right angle with respect to the phase velocity vectors vt, -v!, and component formation due to the reflected return waves of the surface acoustic waves at these end surfaces is made. The effect on the illusion signal is minimized.

That is, the phase velocity vector vl+vZ of the surface acoustic wave in the surface acoustic wave generation region and the phase velocity vector Vll+VZ□ of the surface acoustic wave in the surface acoustic wave propagation region are nonparallel, and the end face direction vector of the gate electrodes 5c and 5d is If e, the inner product is ■,・e≠0, and v
1 awakening e≠0.

In addition, as a surface acoustic wave, a surface acoustic wave generation area (input ID
Sezawa waves are used in both the T 4e and 4f production regions) and the surface acoustic wave propagation region, and the film thickness of the piezoelectric layer in the input IDT 4e and 4f production regions is set to kh = 1.5 (k is the wave number = 2π/
λ), the thickness of the piezoelectric layer in the surface acoustic wave propagation region is kh=
It is 3.0.

As a result, the phase velocities of the input TDT 4e and 4f fabrication regions and the surface acoustic wave propagation region are 5500 m/s and 4
900 m/s, which is a wavelength difference of about 12% in both regions.

More specifically, frequency 2G)lz, delay time 10μs
The width of input IDTs 4e and 4f is approximately 0.7 μ.
It is m. On the other hand, there is a gate electrode 5 in the propagation path of the surface acoustic wave.
c.

5d is formed, the phase velocity of the surface acoustic wave is 4
It becomes even smaller to about 800 m/s. Therefore, a propagation path length of about 48 mm could be fabricated. Also, at this time, the electromechanical coupling constant is 2, which is 3 in the input IDT 4e and 4f fabrication regions.
．． 5%, and 3.7% in the propagation path, which is a practical size.

The thickness of the Si/Si'' substrate 1d/lc used as the substrate is at least twice the wavelength of the surface acoustic wave in the surface acoustic wave generation region, that is, the wavelength in the region where the wavelength of the surface acoustic wave is longer. It is preferable.

In other words, if the thickness of the Si/Si' substrate 1d/lc becomes twice or less, the phase velocity of the surface acoustic wave propagating through Zn0 3c will be easily influenced by the Si/Si' substrate 1d/lc. It is.

In the above Example-1, Zn03c is used as the piezoelectric layer.
, a Si/Si” substrate 1d/l as a layer without piezoelectricity
c was used, but there is no problem in using materials other than these. In addition, this example uses a combination of materials in which the phase velocity of surface acoustic waves in a material that does not have piezoelectricity is larger than the phase velocity of surface acoustic waves in a piezoelectric material, and has piezoelectricity in the surface acoustic wave generation region. Although the structure is such that the thickness of the layer is smaller than the thickness of the piezoelectric layer in the surface acoustic wave propagation region, the following combinations are possible in addition to this combination.

■By using a combination of materials in which the phase velocity of surface acoustic waves in non-piezoelectric materials is smaller than the phase velocity of surface acoustic waves in piezoelectric materials, the film thickness of the layer with piezoelectricity in the surface acoustic wave generation region is determined. , a configuration in which the thickness is greater than that of the piezoelectric layer in the surface acoustic wave propagation region.

■By using a combination of materials in which the phase velocity of surface acoustic waves in the non-piezoelectric material is larger than the phase velocity of the surface acoustic waves in the piezoelectric body, a film of a layer without piezoelectricity in the surface acoustic wave generation region is used. A configuration in which the thickness is thicker than the thickness of the layer without piezoelectricity in the surface acoustic wave propagation region.

■By using a combination of materials in which the phase velocity of the surface acoustic waves in the non-piezoelectric material is smaller than the phase velocity of the surface acoustic waves in the piezoelectric body, A structure in which the film thickness is smaller than the film thickness of a layer without piezoelectricity in the surface acoustic wave propagation region.

(2) Example-2 FIG. 3 is a diagram explaining Example-2, in which (a) is a cross-sectional view of a semiconductor convolver, and (b) is a plan view.

In Example 2, a thermally oxidized Si'' substrate 1e is etched to remove the 5iO 72c in the surface acoustic wave propagation region (propagation path), and then GaA is etched only in the propagation path via a strained superlattice 9.
A PN junction of s10 is formed by epitaxial growth. Next, Si is applied as a charge insulating layer and a diffusion prevention layer.
The O□ layer 2c and the Zn0 layer 3d as a piezoelectric layer are sputtered in this order. And finally, input ID 74g
, 4h and gate electrodes 5e and 5f are formed.

Further, the angle formed by the surface acoustic wave input side side of the GaAs layer 10 and gate electrodes 5e and 5f and the phase velocity vector of the surface acoustic wave is deviated from 90'' and is oblique, and the elastic surface at this end surface The influence of reflected return waves on the convolution signal is minimized.

By the way, the phase velocity of surface acoustic waves in GaAs is 2
The speed is about 700m/s. Therefore, with the above configuration, the phase velocity of the surface acoustic wave in the propagation path is 4000 m.
/s or less, and can be reduced to a minimum of about 2700 m/s (depending on the thickness of GaAs). On the other hand, the propagation path length is 27mm
~40 cabinets, and it is possible to make the external shape even smaller than in Example-1.

The thickness of the Si'' substrate 1e used as the substrate is preferably at least twice the wavelength of the surface acoustic wave in the surface acoustic wave generation region, that is, the wavelength in the region where the wavelength of the surface acoustic wave is longer. That is, if the thickness of the St+ substrate 1e becomes twice or less, the phase velocity of the surface acoustic wave propagating through the Zn0 3d will be easily influenced by the Si'' substrate 1e.

In the above Example-2, Zn03d is used as the piezoelectric layer.
, Si”le and GaAs1 as layers without piezoelectricity
0 was used, but there is no problem in using materials other than these.

(3) Example-3 FIG. 4 is a plan view of a semiconductor convolver explaining Example-3.

In Example-3, (1
120) Zn0 3e by RF sputtering method, CVD
The input IDTs 4i and 4j are grown epitaxially to a thickness h of kh=2.0 by a method such as
1> direction of primary Rayleigh waves 12a, 12b (phase velocity #
5,500 m/s) or a high-order Rayleigh wave (Sezawa wave: phase velocity > 5,500 m/s) is determined and manufactured.

The semiconductor convolver of this embodiment has an input IDT 4r.

After the surface acoustic wave excited by 4j propagates in the <ooot> direction, it is reflected by the reflecting surfaces 11a and llb, and in the propagation region, love waves 13a and 13 propagate in the <1100> direction.
b (phase velocity -3400 m/s).

In other words, the phase velocity changes from a Rayleigh wave with a phase velocity of 5500 m/s to 340 m/s in the mode conversion regions 14a and 14b.
' Converted to a love wave of Om/s.

In the propagation region, a gate electrode 5g and a Zn
A GaAs layer is formed between the O layer 3e and the sapphire substrate, and as a result, the phase velocity of the surface acoustic wave in the propagation region is further reduced, and the propagation path length can be shortened to nearly 30 mm in an element with a delay time of 10 μs. It becomes possible to do so.

In the above Example-3, the Zn0 layer 3 is used as the piezoelectric layer.
e. Although GaAs and sapphire were used as the layer without piezoelectricity, there is no problem in using materials other than these.

In this Example-3, among the same type of surface acoustic waves, a low-order surface acoustic wave with a small phase velocity is used in the propagation region, and a high-order surface acoustic wave with a large phase velocity is used for surface acoustic wave generation NM. May be used in Furthermore, the reflective surfaces 11a and llb in the same embodiment are essentially the same even if refraction is used.

(4) Example-4 Another aspect of the features of the present invention is that it is possible to realize a surface acoustic wave with a higher energy density than ever before in the propagation path, or a surface acoustic wave with a shorter wavelength than ever before. can be raised.

Therefore, improvements in the efficiency of devices that use strain nonlinearity, improvements in the efficiency of devices that use nonlinearity due to high-order physical parameters such as piezoelectric constant and dielectric constant, miniaturization of delay elements, and improvements in the efficiency of devices that use optical diffraction using surface acoustic waves. Various applications are possible, such as improving diffraction efficiency and shortening wavelength.

An example of this is an optical diffraction device.

FIG. 5 is a diagram illustrating Example 4, in which (a) is a perspective view of an optical diffraction device, and (b) is a diagram illustrating light diffraction.

In Example-4, an ID is placed on a piezoelectric substrate 3f made of liquid-touch crystal.
The wavefront 19a of the surface acoustic wave excited by the ID 74k forms a refractive index lattice pattern in the optical waveguide I8, and propagates through the optical waveguide 18. This is an optical diffraction device that diffracts incident light 15.

That is, FIG. 5(b) shows a case where an optical surface wave propagating in the X direction is diffracted by a surface acoustic wave propagating in the x IF force direction, and diffracted light 17 is generated in the X direction.

In co-mode diffraction, the diffracting angle θ (θ.

=θ, =θ, , ) are given by the following equation (8).

θ, -5in-' (K/2β) ---(81
However, β is the phase constant of the mode for the diffracted light 17, K is the wave number of the surface acoustic wave, and IKl=2π/λ.

Therefore, by using Examples 1 to 3 and shortening the wavelength of the surface acoustic wave propagating on the piezoelectric substrate 3f, an optical diffraction device that can obtain high diffraction efficiency for light with a short wavelength can be created. realizable.

〔Effect of the invention〕

As described above, according to the surface acoustic wave element of the present invention, the phase velocity of the surface acoustic wave in the surface acoustic wave generation region is increased (,
On the other hand, the phase velocity of the surface acoustic wave in the surface acoustic wave propagation region can be reduced.

Therefore, it becomes possible to widen the 1070 width for exciting surface acoustic waves, and the IDT becomes easier to manufacture. Furthermore, the length of the surface acoustic wave propagation region can be shortened, and the surface acoustic wave element can be downsized.

That is, it is possible to obtain a small-sized surface acoustic wave device that is easy to manufacture while increasing the frequency of the surface acoustic wave device.

As a result, it is possible to realize a surface acoustic wave device that is small, inexpensive, and enables high-quality communication.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view explaining the basic principle of the present invention, FIG. The figure shows Example-2
, (a) is a cross-sectional view of a semiconductor convolver,
(b) is a plan view, FIG. 4 is a plan view of a semiconductor convolver for explaining Example-3, FIG. 5 is a view for explaining Example-4, and (a) is a perspective view of an optical diffraction device. , (b) is a diagram for explaining light diffraction, and FIG. 6 is a diagram for explaining a semiconductor convolver. (a) is a cross-sectional view of the semiconductor convolver, and (b) is a plan view. In the figure, la, ld are Si, lc, le are Si"
, lb is a non-piezoelectric layer, 2a, 2b, 2c are 5iOz, 3
a, 3c, 3d, 3e, ZnO13b is a piezoelectric layer, 3f is a piezoelectric substrate, 4a, 4b, 4c, 4d4e
, 4f, 4g, 4h, 4i, 4j are input IDTs,
4 has IDT, 5a. 5b, 5c, 5d, 5e, 5f, 5g are gate electrodes, 6
a, 6b+ 6c, 6d. 6e, 6f are output terminals, 7a, 7b, 7c, 7d
is a surface acoustic wave generation region, 8a and 8b are surface acoustic wave propagation regions, 9 is a strained superlattice, and 10 is GaAs, lla, llb
is a reflective surface, 12a, 12b are Rayleigh waves, 13a, 1
3b is a love wave, 14a and 14b are mode conversion regions, 1
5 is the incident light, 16 is the non-diffracted light, 17 is the diffracted light, 18 is the optical waveguide, 19 is the surface acoustic wave, 19a is the wavefront of the surface acoustic wave, 20.21 is the traveling direction of the surface acoustic wave, and 22 is the depletion layer. ,
are shown respectively. Patent applicant Fujitsu Co., Ltd. sub-agent Patent attorney Yasufumi Fukushima (=l) (b') Fushin σ11-/ 2nd concave invention Atsuho Katari station Meikyou 1st ward (b) Fu Farting 1-2 3rd employment example-3 4th z (d) (b') :)

Claims (4)

[Claims] 1. A piezoelectric layer (3b) and a non-piezoelectric layer (1
b), and consists of surface acoustic wave generation regions (7c, 7d
) and a surface acoustic wave propagation region (8b), the thickness of the piezoelectric layer (3b) and the non-piezoelectric layer (3b)
1b), the thickness of at least one layer is between the surface acoustic wave generation region (7c, 7d) and the surface acoustic wave propagation region (7c, 7d).
8b), the phase velocity (v_1, v_2) of the surface acoustic wave in the surface acoustic wave generation region (7c, 7d) is changed to the phase velocity (v_1_1, v_1, v_2) of the surface acoustic wave in the surface acoustic wave propagation region (8b).
v_2_2) A surface acoustic wave element characterized by: being larger than v_2_2). 2. A piezoelectric layer (3b) and a non-piezoelectric layer (1
b), and consists of surface acoustic wave generation regions (7c, 7d
) and a surface acoustic wave propagation region (8b), and the type of piezoelectric layer (3b) and the non-piezoelectric layer (3b).
Among the types 1b), at least one layer has a surface acoustic wave generation region (7c, 7d) and a surface acoustic wave propagation region (7c, 7d).
8b), the phase velocity (v_1, v_2) of the surface acoustic wave in the surface acoustic wave generation region (7c, 7d) is changed to the phase velocity (v_1_1, v_1, v_2) of the surface acoustic wave in the surface acoustic wave propagation region (8b).
v_2_2) A surface acoustic wave element characterized by: being larger than v_2_2). 3. A piezoelectric layer (3b) and a non-piezoelectric layer (1
b), and consists of surface acoustic wave generation regions (7c, 7d
) and a surface acoustic wave propagation region (8b), and the surface acoustic wave propagation mode in the surface acoustic wave propagation region (8b) is different from the surface acoustic wave propagation mode in the surface acoustic wave generation regions (7c, 7d). The phase velocity (v_1, v_2) of the surface acoustic wave in the surface wave generation region (7c, 7d) is expressed as the phase velocity (v_1_1, v_2) of the surface acoustic wave in the surface acoustic wave propagation region (8b).
v_2_2) A surface acoustic wave element characterized by: being larger than v_2_2). 4. In the surface acoustic wave device according to claims 1 and 2, a surface acoustic wave passes through the boundary between the surface acoustic wave generation region (7c, 7d) and the surface acoustic wave propagation region (8b). A surface acoustic wave element characterized in that the direction of the previous phase velocity is different from the direction of the phase velocity after passing through the device.