JPH08130434A - Surface acoustic wave element - Google Patents

Abstract

PURPOSE: To provide an acoustic charge transmission(ACT) element by preparing the surface acoustic wave(SAW) element equipped with a semiconductor layer formed to partially contain a hetero junction layer on an Si substrate at least. CONSTITUTION: A buffer layer 1a is formed on an Si substrate 1 the resistivity of which is larger than 2000Ω.cm and further, hetero junction layers 1b and 1b are formed on it. Electrodes 3 and 4 are formed on a cap layer 1c composed of a GaAs layer or the like. The hetero junction layers are provided with the configuration of a single hetero layer (DaAs/Alx Ga1-x As) or double hetero layer (Alx Ga1-x As/GaAs/Alx Ga1-x As).

Description

Detailed Description of the Invention

[0001]

The present invention relates to surface acoustic waves (SAW:
The present invention relates to a surface acoustic wave element, and particularly to a so-called monolithic surface acoustic wave element formed by forming a piezoelectric film on a semiconductor substrate.

[0002]

2. Description of the Related Art A surface acoustic wave (SAW) element occupies an important position as a signal processing device because it has a high-frequency signal storage function and a high-speed batch processing function. Further, it is integrated with a semiconductor device on the same substrate. In the monolithic integrated device that has been realized, many functions such as amplification and multiplication that can be realized by a semiconductor element are added, and the function is becoming multifunctional.

At present, there are roughly two types of proposals for the configuration of a monolithic multifunction integrated SAW device. One is a laminated structure in which a piezoelectric thin film such as ZnO or AlN is formed on a Si semiconductor substrate, and the other is a structure in which a SAW device and a semiconductor device are integrated on a GaAs substrate which is a piezoelectric semiconductor.

III-V group compound semiconductors such as GaAs are
Compared with Si, it has the following electrical, acoustic, and optical characteristics. a) Electron mobility several times higher than that of Si b) Electric conductivity can be controlled in a wide range from semi-insulating to conductive c) Piezoelectricity d) Light emission and light receiving element from visible to infrared can be created With the recent remarkable development of III-V compound semiconductor thin film forming technology, it is possible to form a heterostructure element represented by GaAs / AlGaAs, and it has been confirmed that a device utilizing the quantum effect has an excellent function.

[0005]

SUMMARY OF THE INVENTION As described above, GaA
s has many functions that Si does not have, but conventional Zn
In a composite device of a piezoelectric thin film such as O or AlN and Si, there is a limit to the multifunctionalization of the element. The problems of the SAW device using GaAs are that the increase in the diameter of the wafer is still insufficient, there is a problem in productivity, and the substrate cost is high.

[0006]

OBJECTS OF THE INVENTION It is a primary object of the present invention to provide a basic element structure for enabling multifunctionalization of a monolithically integrated SAW device including functions such as advanced and widespread ACT elements.

[0007]

To achieve the above object, the surface acoustic wave device of the present invention comprises a Si substrate having a predetermined resistivity and a heterojunction layer at least partially on the Si substrate. The gist of the present invention is to include a semiconductor layer formed on the semiconductor layer, and electrode means formed on the semiconductor layer and including at least a surface acoustic wave excitation electrode.

The surface acoustic wave device of the present invention has the following modifications. (I) Electrodes other than the surface acoustic wave excitation electrode are formed on the semiconductor layer corresponding to the heterojunction layer. (Ii) As the Si substrate, a high-resistance Si substrate having a resistivity of 2000 Ω · cm or more was used. (Iii) The heterojunction layer is a single heterojunction layer. (Iv) The single heterojunction layer is GaAs / Al _x Ga
_It has a structure of _1-x As. (V) The heterojunction layer is a double heterolayer. (Vi) The double hetero layer is Al _x Ga _1-x As / GaA
s / Al _x Ga _1-x As. (Vii) The surface acoustic wave excited by the electrode is of the second Rayleigh mode, the wavelength of the surface acoustic wave is λ, the thickness of the semiconductor layer is H, and k = 2π / λ,
It was set to 1.5 <kH <2.5. (viii) The surface acoustic wave excited by the electrode is of the first Rayleigh mode, the wavelength of the surface acoustic wave is λ, the thickness of the semiconductor layer is H, and k = 2π / λ, and k
H ≧ 3.0.

[0009]

In the surface acoustic wave element of the present invention, since the semiconductor layer includes the heterojunction layer, a potential well is formed in the layer, and in the ACT element, electrons as signal charges are injected into this potential well. And acts as a channel layer.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG.
Shows the basic structure of a GaAs / Si SAW element. Ga
As is a piezoelectric semiconductor material, and the piezoelectric effect can be put to practical use in a semi-insulating substrate or a depletion region. The velocity and electromechanical coupling coefficient of SAW propagating in the <110> direction of a GaAs single crystal (100) substrate are 2868 m / s, respectively.
s, 0.72%. 1 is a Si (100) substrate, on which a GaAs piezoelectric semiconductor thin film 2 is MO
It is formed by the CVD method. The GaAs film is an epitaxial film, and the (100) plane grows. Further GaA
The SAW excitation / reception transducers 3 and 4 are provided on the upper surface of the piezoelectric semiconductor thin film 2. The propagation direction of SAW is S
The directions are substantially parallel to the i <110> and GaAs <110> directions. In the epitaxial growth of a GaAs thin film, since a Si substrate having a slight off angle is often used, it means that the plane orientation and direction described here are the closest to it, and it is considered to have a certain width. Good. GaAs piezoelectric semiconductor thin film 2 is non-doped GaAs
And, its specific resistance is designed to be high. Undoped GaA
Since the s-piezoelectric semiconductor thin film 2 has a sufficiently high specific resistance, it exhibits a sufficient piezoelectricity, but there are the following two means for further increasing the specific resistance of the film. 1) After forming a GaAs piezoelectric semiconductor thin film, the GaAs film is made semi-insulating by proton impact. 2) A SAW transducer is composed of Schottky electrodes, and a DC bias is applied to extend a depletion layer below the electrodes.
Whichever method is used, the piezoelectricity of GaAs can be maximized.

The graph of FIG. 2 shows the relationship between the phase velocity Vp of the SAW propagating in the GaAs / Si structure and the film thickness H of the GaAs film. k is the SAW wave number (k = 2π / λ, λ
Is the wavelength of SAW). In the GaAs / Si laminated structure, G
This is much faster than the sound velocity of aAs single crystal, and in realizing a high-frequency SAW element, the cycle length of the transducer is long, and the effect of facilitating photolithography processing is exhibited. Further, in the range of kH ≧ 0.7, the second Lely mode, that is, the Sezawa wave exists, and the phase velocity thereof is further large.

The graphs of FIGS. 3 and 4 show GaAs / S.
The GaAs film thickness dependence of the electromechanical coupling coefficient of the SAW transducer formed on the i structure is shown. FIG. 3 shows the case of the first release mode, and FIG. 4 shows the case of the second release mode. Two types of SAW transducer configurations are shown. One is a configuration in which the Si substrate 1 has a relatively high specific resistance and the electrodes 3 and 4 are provided on the GaAs surface. With this structure, a large coupling coefficient can be obtained when the GaAs film is relatively thick. The other is the case where the electrodes 3 and 4 are formed on the GaAs surface and the high-concentration impurity diffusion region 5 is provided on the surface of the Si substrate 1 below the electrodes. A large coupling coefficient is obtained. A particularly noteworthy characteristic is that, in the latter transducer configuration, the layered structure provides a coupling coefficient larger than that of a single crystal GaAs substrate.

In the latter transducer configuration,
Although the high-concentration impurity diffusion region is provided only under the electrode, a similar coupling coefficient can be obtained by using a low-resistance Si single crystal substrate.
However, the major feature of the GaAs / Si structure is that Si
Alternatively, since the semiconductor element can be integrated in the GaAs region, the resistivity of the Si substrate is usually selected so that the characteristic of the semiconductor element to be integrated is the best as shown here. In order to increase the receiving efficiency of
A high-concentration impurity diffusion region is often provided below the transducer electrode.

The following can be understood from the graphs of FIGS. 2, 3 and 4. a) In the SAW functional device having the GaAs / Si structure, it is better to use the second Rayleigh mode. b) The phase velocity is much higher than that of the single crystal GaAs substrate, and it becomes easy to increase the frequency. c) The coupling coefficient can be larger than that of the single crystal GaAs substrate. As described above, the acoustic characteristics of the GaAs / Si structure can further improve the characteristics of the single crystal GaAs substrate.

The GaAs / Si structure of FIG. 1 exhibits acoustic characteristics that exceed those of a single crystal GaAs substrate. However, the coupling coefficient is as small as about 0.08%, which may limit the application to functional devices. In the embodiment shown in FIG. 5, a ZnO piezoelectric film 6 is further formed on the GaAs / Si structure, and excitation / reception SAW transducers 3 and 4 are formed on the surface of the ZnO piezoelectric film 6 to improve the coupling coefficient. There is.

Also in the above structure, as in the case of FIG. 1, there are first and second Lely modes, and the coupling coefficient thereof is ZnO / S.
An extremely large coupling coefficient comparable to the i structure is obtained. In this embodiment, considering the integration of semiconductor elements, attention is paid only to improving the excitation / reception efficiency of the transducer of the first embodiment, and the ZnO piezoelectric thin film 6 is formed only in the SAW transducer portion. .

Although various configurations of the transducer are possible, examples of configurations having particularly high excitation and reception efficiency are shown in FIGS. 6 and 7.
Shown in In FIG. 6, the metal electrode 7 is formed at the interface between the ZnO film 6 and the GaAs film 2, and in FIG. 7, the high-concentration impurity diffusion region 5 is provided on the surface of the Si substrate 1. Both are ZnO
Comb-shaped input / output transducer electrodes 3, 4 on the surface of the piezoelectric film
Is provided. The metal electrode 7 and the high-concentration impurity diffusion region 5 are usually formed only under the transducer. Figure 6
And the transducer configuration shown in FIG.
Large electrical coupling coefficient is obtained in the Rayleigh mode.

Acoustic charge transfer (ACT: Acoustic Charge), which is a high-speed signal processing device similar to a GaAs CCD.
(Transport) element has recently received attention. The CW-excited SAW becomes a clock signal, traps charges in the potential well of the SAW, and transfers the charges in synchronization with the SAW speed. An extremely high-speed charge transfer device can be realized without the need to form a clock gate electrode like a GaAs CCD. The transferred charge is a non-destructive sensing tap (Non-Destructive Sens
ing tap) to sequentially detect the gain
It is weighted by a gate FET and the sum is output. The delay and product-sum operations are performed at high speed, and an ideal transversal filter function is realized by the ACT element.
The signal processable band of the element is limited by the SAW frequency / 2 (Nyquist frequency) regardless of the frequency characteristics of the SAW transducer, and has a very large band. The delay is determined by the SAW speed and the device length, and a relatively large delay amount is realized. Therefore, the time band product, which is an index of the processability of the signal processing element, is extremely large. References on the operation of ACT include: a) MJHoskins, et.al. "Charge Transport by surface
acoustic waves in GaAs ", Appl.Phys.Lett., 41 (4), pp.3
32-334,1982. B) WJ Tanski, et.al. "Heterojunction Acoustic Char
ge Transport Deviceson GaAs ", Appl.Phys.Lett., 52
(1), pp.18-20, 1988. and so on.

FIG. 10A is a diagram showing the basic structure of such an ACT element. High resistance (eg 2000Ω ・
buffer layer 1 on Si substrate 1 of cm or more)
a is formed, and the heterojunction layer 1b is further formed on the layer a. Reference numeral 1c is a cap layer made of GaAs or the like, and the electrodes 3 and 4 are formed on this layer. The heterojunction layer is a single heterolayer (eg, GaAs / Al _x Ga _1-x A
s) or double hetero layer (eg Al _x Ga _1-x As /
Any structure of GaAs / Al _x Ga _1-x As) can be adopted. The GaAs portion in these heterojunction layers acts as a channel layer. 10 (b) and FIG.
The configuration of each junction layer and the schematic characteristic diagram of the potential well generated by it are shown in (c). In the above characteristic diagram, the vertical axis represents the conduction band energy level and the horizontal axis represents the depth from the surface to the substrate. It can be seen that potential wear is formed on the interface between GaAs and Al _x Ga _1-x As and on the GaAs layer. In the ACT element, electrons, which are signal charges, are injected into this potential well, and it operates as a so-called channel layer.

FIG. 8 shows an embodiment of the ACT device having the heterojunction layer shown in FIG. 10 (c).
The configuration and operating principle will be described. Si (100) substrate 1
Then, the GaAs piezoelectric semiconductor thin film 2 is formed. Although the GaAs piezoelectric semiconductor thin film 2 is non-doped GaAs, the GaAs layer 2 is made semi-insulating by proton impact in order to maximize its piezoelectricity. Then undoped Al _x G
The a _1-x As layer 8 is formed. Further, a non-doped GaAs transfer channel layer 9 is formed, followed by n-type Al _x Ga _1-x A
The s charge supply layer 10 is formed. Al _x Ga _1-x liquid crystal Al
By setting the molar ratio to about 0.3, GaAs / AlxG
The energy gap of the conduction band at the _a1-x As interface is 0.25.
It becomes eV, and an energy gap is formed in a band structure. That is, Al _x Ga _1-x As / GaAs / Al _x G
A double heterojunction is formed by the laminated structure of a _1-x As. The transferred charges are electrons, and the electrons are confined in the non-doped GaAs transfer channel layer 9. In the structure of FIG. 8, a non-doped GaAs cap layer 11 is further formed. The double heterojunction layers 8 to 11 formed on the GaAs piezoelectric semiconductor film 2 may have a very small film thickness, and the total film thickness is at most 2000 to 300.
0 Å, and especially the non-doped GaAs transfer channel layer 9 is formed at a position of only about 1000 Å from the element surface, and is formed at a position extremely close to the surface. The double heterojunction layers 8 to 11 leave the transfer channel region,
Alternatively, the SAW transistor portion is removed by mesa etching.

Reference numeral 12 is a unidirectional transducer for CW excitation formed in a region where the double heterojunction layers 8 to 11 are removed. Usually, a comb-shaped electrode composed of a Schottky electrode and a SAW propagation direction are opposite to each other. SA at the position
It consists of a W grating reflector. Reference numeral 13 denotes an input diode for inputting a signal, which includes an ohmic electrode 13a and a Schottky electrode 13b. Electrons are injected by this input diode. Reference numeral 14 is a nondestructive sensing tap Schottky electrode formed on the transfer channel, which nondestructively detects a packet of electrons transferred in the channel. 15
Is an ohmic electrode for taking out the transferred electrons.

FIG. 11 shows a film thickness H of a compound semiconductor layer (generally made of GaAs, Al _x Ga _{1 -x} As layer) including a heterojunction formed on the Si substrate 1 in the ACT element having the structure of FIG. Also 1.5 <kH <2.5 (k = 2π / λ,
λ is set to the propagating SAW wavelength) and S in the signal transfer unit when the second Rayleigh mode (that is, the Sezawa wave) is used
It is a diagram illustrating a profile in the depth direction kH ₃ elements of AW potential. Two Al _x Ga _1-x As layers 8, 10
The GaAs layer sandwiched by is the channel layer 9. ACT
In the device, electrons are confined in the SAW potential well, and the SAW propagation velocity is synchronized and transferred.
It is desirable that the magnitude of the AW potential is large. The potential value on the vertical axis indicates the case where the SAW power is 1 mW / mm. The distribution of the solid line is 200 for the Si substrate.
The case where a high resistance substrate of 0 Ω · cm or more is used is shown. It was confirmed that the potential value in the channel layer was about 0.08 V, which was a sufficient value. Further, the broken line shows the characteristics when a high-concentration diffusion region n ⁺ layer (100) is further added to the Si substrate surface as shown in FIG. Such n ⁺
It can be seen that the layers can easily be formed on the substrate before the GaAs layer 8 is formed, which further improves the value of the potential. As described above, it was confirmed that by using the Sezawa wave, which is a characteristic of the laminated structure, the element can be formed with a relatively thin film thickness, and moreover, the characteristics that are higher than those obtained when the conventional GaAs substrate is used can be obtained.

FIG. 13 shows the SAW potential depth direction in the transfer channel portions 8 to 11 of the device in the configuration of FIG. 8 when the fundamental wave (1st Rery wave) is used as the propagating wave and kH> 3.0. It is a kx ₃ profile. By increasing the total film thickness, the SAW characteristics of the laminated structure
It shows the same characteristics as a GaAs single crystal substrate, and as shown in the figure, a sufficient potential value of about 0.08
V has been realized. That is, by taking the above configuration,
While using a Si substrate that is inexpensive and suitable for mass production as a substrate, it has been possible to achieve characteristics comparable to those of a GaAs single crystal substrate.
The transducer 12 is not necessarily the heterojunction layer 8 to
Instead of being provided on the GaAs semiconductor thin film 2 from which 11 is removed, it may be provided on the heterojunction layer. In this case, it is preferable that at least the portion of the heterojunction layer below the transducer 12 be semi-insulating. Further, electrodes other than the SAW excitation electrode need to be provided on the semiconductor layer corresponding to the heterojunction layer.

The actual device operation will be further described with reference to FIG. 9 which is a plan view of the device. CW as clock signal
Electrode 12a and reflector 1 to excite the SAW of
The CW signal having the clock frequency fo is input to the unidirectional transducer 12 configured by 2b to excite the CW SAW propagating in the right direction in FIG. The signal to be signal-processed is input to the input diode 13. Input diode 1
Although 3 is composed of an ohmic electrode 13a and a Schottky electrode 13b, the ohmic electrode 13a is normally grounded and a signal is input to the Schottky electrode 13b. An appropriate DC reverse bias V _B is applied to the Schottky electrode 13b in order to set a steady amount of electrons in the packet when no signal is input, and the RF signal f is applied to this potential.
(T) is added. The input diode 13 has a lateral Schottky diode configuration. The potential of the Schottky electrode 13b determines the level of the depletion layer under the diode, and when the SAW potential passes under the input diode, the amount of electrons drawn into the potential well depends on the input signal. . In this way, the electric signal is converted into the charge amount (electron amount). Since the SAW propagates continuously, the conversion into the electric charge is repeated every cycle of the SAW, the input signal is automatically sampled, and the charge packet trapped in the valley of the SAW potential is formed. Since the SAW is a continuous wave (CW), for example, a sine wave, its potential shape is sinusoidal, and each charge packet is separated for each cycle of the potential of the SAW. It has been locked up.

The charge packet sampled by the input diode is transferred in the channel in synchronization with the SAW speed. Since the vertical direction of the channel has the double hetero structure as shown in FIG. 8, electrons are confined and transferred in the potential well (in the GaAs transfer channel layer) formed by the heterojunction. The lateral charge confinement can be achieved by proton-impacting the regions other than the channel region shown by the broken line in FIG. 9 to make them semi-insulating to separate the channels, or by removing the double hetero layer other than the channel region by mesa etching. Since charges are confined in three directions in this manner, the charge transfer device having this structure can realize extremely high charge transfer efficiency.

The charge packet transferred in the channel is non-destructively detected by the Schottky electrode 14. There are two detection methods, voltage detection and current detection, which can be distinguished by the load connected to the Schottky electrode. Capacitive load is used for voltage detection, and resistive load is used for current detection. In each case, a signal corresponding to the amount of electrons in the charge packet is similarly obtained. The Schottky electrodes 14 are provided at a certain interval. When the SAW delay time between taps 0 to N−1 is τ and the input signal is f (t), the nth tap output is (t−nτ ) Is a sample value of an input signal having a delay time corresponding to the positions of taps 0 to N-1.

The outputs of the respective taps are weighted and then combined to form an output. The weighting is performed by multiplying the stored weighting factors h _{0 to} h _N−1 by the multiplier 14a and the tap output, and the multiplier 14a is a dual gate GaAs.
It can be realized with FET. Ohmic electrode 1 on the right edge of the device
5 is provided, and the transferred electrons are taken out of the device by the ohmic electrode 15. The basic structure of the device is a structure in which a GaAs / AlGaAs heterojunction is formed on a GaAs / Si structure, and a SAW transducer, an input / output diode, and a nondestructive sensing tap are provided. In this structure as well, as in the embodiment of FIG. 5, the ZnO piezoelectric film can be formed only on the transducer portion in order to improve the excitation efficiency of the transducer. As a result, the transducer input power can be reduced, and as a result, low power consumption of the element can be achieved.

[0028]

As described above, according to the present invention, G
An acoustic charge transfer device, which is a high-speed signal processing device, can be realized by providing an aAs / Si structure as a base and providing a hetero structure on the aAs / Si structure. The effects of using GaAs / Si as the basic structure are summarized below. a) Cost reduction is possible by using Si substrate. b) Wafer diameter can be increased. c) In particular, by utilizing the second Rayleigh mode, a coupling coefficient larger than that of single crystal GaAs can be utilized. Further, by forming a ZnO piezoelectric thin film on the transducer part, a larger coupling coefficient can be utilized. This leads to a reduction in the input power of the SAW CW serving as a clock signal, resulting in a significant reduction in power consumption. Also, at the same input power,
Since this leads to an increase in the potential strength of the SAW, the charge capacity will increase, and as a result, the dynamic range can be expected to expand. d) In the acoustic charge transfer device, by completing many functions such as signal detection, sum-of-products calculation, and memory of weighting factors on one chip, the degree of perfection of the device is increased. A high-speed low-power consumption integrated device can be realized by configuring a high-speed operation unit such as a product-sum operation with a GaAs semiconductor device and a memory and a logic circuit with Si-CMOS logic.

[Brief description of drawings]

FIG. 1 is a side view of a surface acoustic wave device which is the basis of the device of the present invention.

FIG. 2 is a graph showing the dependence of SAW phase velocity on a GaAs thin film.

FIG. 3 is a graph showing a coupling coefficient of a first Rayleigh mode of a GaAs / Si structure.

FIG. 4 is a graph showing a coupling coefficient of a second Rayleigh mode of a GaAs / Si structure.

FIG. 5 is a side view of another surface acoustic wave device which is the basis of the device of the present invention.

FIG. 6 is a side view showing an improved example of the surface acoustic wave element of FIG.

FIG. 7 is a side view showing another modified example of the surface acoustic wave element of FIG.

FIG. 8 is a side view of the ACT element of the present invention.

FIG. 9 is a plan view for explaining the operation of the ACT element of the present invention in detail.

FIG. 10A is a side view showing the basic structure of the ACT element of the present invention. 10B is a diagram schematically showing an example of a heterojunction layer applicable to the ACT element of FIG. 10A and a potential well generated thereby. 10C is a diagram schematically showing an example of another heterojunction layer applicable to the ACT element of FIG. 10A and a potential well generated thereby.

11 is a diagram showing potential characteristics of the ACT element of FIG.

FIG. 12 is a side view showing an improved ACT of the present invention.

13 is a diagram showing potential characteristics of the ACT element of FIG.

[Explanation of symbols]

1 Si Substrate 2 GaAs Piezoelectric Semiconductor Film 3 Input Transducer 4 Output Transducer 5 Si High-Concentration Impurity Diffusion Region 6 ZnO Piezoelectric Thin Film 7 Metal Electrode 8 Al _x Ga _1-x As Layer 9 GaAs Transfer Channel Layer 10 Al _x Ga _1-x As Charge supply layer 11 GaAs cap layer 12 Transducer for unidirectional SAW excitation 13 Input diode 14 Nondestructive sensing tap / Schottky electrode 15 Ohmic electrode

Claims (9)

[Claims] 1. A Si substrate having a predetermined resistivity, a semiconductor layer formed on the Si substrate so as to at least partially include a heterojunction layer, and at least a surface acoustic wave formed on the semiconductor layer. A surface acoustic wave device comprising: an electrode means including an excitation electrode; 2. The surface acoustic wave device according to claim 1, wherein electrodes other than the surface acoustic wave excitation electrode are formed on a semiconductor layer corresponding to the heterojunction layer. 3. The Si substrate has a resistivity of 2000Ω.
The surface acoustic wave device according to claim 1, wherein a Si substrate having a high resistance of cm or more is used. 4. The surface acoustic wave device according to claim 1, wherein the heterojunction layer is a single heterojunction layer. 5. The single heterojunction layer is GaAs /
The surface acoustic wave device according to claim 4, wherein the surface acoustic wave device has a structure of Al _x Ga _1-x As. 6. The surface acoustic wave device according to claim 1, wherein the heterojunction layer is a double heterolayer. 7. The double heterolayer is Al _x Ga _1-x As.
7. The surface acoustic wave device according to claim 6, having a structure of / GaAs / Al _x Ga _1-x As. 8. The surface acoustic wave excited by the electrode is of a second Rayleigh mode, the wavelength of the surface acoustic wave is λ, the thickness of the semiconductor layer is H, and k = 2π / λ. , 1.5 <kh <2.5, The surface acoustic wave device according to claim 3, wherein 9. The surface acoustic wave excited by the electrode is of a first Rayleigh mode, the wavelength of the surface acoustic wave is λ, the thickness of the semiconductor layer is H, and k = 2π / λ. , KH ≧ 3.0. The surface acoustic wave device according to claim 3, wherein kH ≧ 3.0.