JP6787553B2 - Piezoelectric element - Google Patents

Description

The present invention relates to a piezoelectric element, and more particularly to a piezoelectric element having high sensitivity and low noise.

In recent years, smartphones, whose demand is rapidly expanding, are often used for microphones that are small and thin and use MEMS (Micro Electro Mechanical System) technology that is resistant to high temperature processing in the solder reflow process of assembly. Further, not only MEMS microphones but also other MEMS elements are rapidly becoming widespread in various fields.

Most of these types of MEMS elements are capacitive elements that capture the vibration displacement of the diaphragm due to acoustic pressure or the like as a capacitance change with the opposing fixed plate, convert it into an electric signal, and output it. However, the improvement of the signal-to-noise ratio of the capacitive element is becoming a limit due to the acoustic resistance caused by the flow of air in the gap between the diaphragm and the fixing plate.

Therefore, a piezoelectric element capable of extracting acoustic pressure or the like as a voltage change due to distortion of a single diaphragm made of a thin film (piezoelectric film) made of a piezoelectric material has been attracting attention.

By the way, it is known that in a piezoelectric element, when there is no acoustic pressure or the like, the residual stress and temperature fluctuation of the piezoelectric film are output as unnecessary signals to deteriorate the characteristics. Therefore, a technique for releasing residual stress by adopting a cantilever structure having one end of a piezoelectric film as a free end is disclosed (for example, Patent Document 1 and the like).

FIG. 6 shows a cross-sectional view of the piezoelectric element having a cantilever structure. As shown in FIG. 6, the piezoelectric films 3a and 3b having a multilayer structure are fixed to the silicon substrate 1 serving as the support substrate via the insulating film 2, and the piezoelectric film 3a is formed by the electrodes 4a and 4b from above and below, and the piezoelectric film 3b is formed. The structure is sandwiched between the electrodes 4b and 4c, respectively. The piezoelectric film and the electrode each have a rectangular planar shape, one end of which is fixed to the silicon substrate 1 and the other end of which is a free end. Further, the electrode 4a and the electrode 4c are connected to one wiring electrode 5a, and the electrode 4b is connected to another wiring metal 5b.

In such a piezoelectric element, when the piezoelectric film 3a is distorted due to acoustic pressure or the like, polarization occurs inside the piezoelectric film 3a, and a voltage signal is extracted from the wiring metal 5a connected to the electrode 4a and the wiring metal 5b connected to the electrode 4b. Is possible. Similarly, when the piezoelectric film 3b is distorted, polarization occurs inside the piezoelectric film 3b, and it becomes possible to extract a voltage signal from the wiring metal 5a connected to the electrode 4c and the wiring metal 5b connected to the electrode 4b.

By the way, it is known that the ratio of the output voltage to the acoustic pressure, that is, the sensitivity of this type of piezoelectric MEMS microphone is lower than that of the capacitive MEMS microphone. In general, the sensitivity of the former is about one tenth or less of that of the latter.

Therefore, an amplifier circuit is required. However, if the configuration includes an amplifier circuit manufactured according to a general method for manufacturing a CMOS semiconductor device, the signal-to-noise ratio is limited to the amplifier circuit. Further, when the piezoelectric element is formed by the CMOS technology having excellent miniaturization, the area occupied by the piezoelectric element that does not require miniaturization is large, which leads to an increase in manufacturing cost. Therefore, it is desired to improve the sensitivity of the piezoelectric element.

Japanese Patent No. 5707323 Japanese Patent Publication No. 2014-515214

The conventional piezoelectric MEMS element has a problem that the sensitivity is lower than that of the capacitive MEMS element. An object of the present invention is to solve such a problem and to provide a piezoelectric element having high sensitivity.

In order to achieve the above object, the invention according to claim 1 of the present application is a piezoelectric element provided with a piezoelectric film whose circumference is fixed to a support substrate and a pair of electrodes arranged so as to sandwich the piezoelectric film. Is composed of a laminated structure including at least a first piezoelectric film and a second piezoelectric film, and includes a plurality of sets of the pair of electrodes arranged with the first piezoelectric film interposed therebetween, and at least the first piezoelectric element and A second piezoelectric element is formed, and a plurality of sets of the pair of electrodes arranged with the second piezoelectric film interposed therebetween are provided, and at least a third piezoelectric element and a fourth piezoelectric element are formed. In addition, the first piezoelectric element and the third piezoelectric element are arranged on the fixed portion side of the piezoelectric film fixed to the support substrate, and the second piezoelectric element and the second piezoelectric element and the third piezoelectric element are arranged on the center side of the piezoelectric film. The fourth piezoelectric element is arranged, the first piezoelectric element and the third piezoelectric element are connected in parallel, and the second piezoelectric element and the fourth piezoelectric element are connected in parallel. and, connecting the before and Symbol first piezoelectric element the second piezoelectric element in series, and that said third piezoelectric element fourth piezoelectric elements are connected in series, said first piezoelectric The element and the third piezoelectric element are vertically symmetrically laminated, and the second piezoelectric element and the fourth piezoelectric element are vertically symmetrically laminated.

According to the second aspect of the present application, in the piezoelectric element according to the first aspect, a plurality of sets of piezoelectric elements including the first to fourth piezoelectric elements are partitioned by a dividing line passing through the center of the piezoelectric film. It is characterized in that it is arranged in each area.

The invention according to claim 3 of the present application is the piezoelectric element according to any one of claims 1 or 2, wherein the set of piezoelectric elements connected in parallel is the front surface or the back surface of the first piezoelectric film or the second piezoelectric film. Alternatively, it is characterized in that it is connected by a continuous extension portion from the electrode of the piezoelectric element arranged between the films.

The invention according to claim 4 of the present application is the piezoelectric element according to any one of claims 1 to 3, wherein when the piezoelectric film is curved and displaced due to vibration, at least for each region partitioned by the bending point of the displacement. Any one of a set of piezoelectric elements composed of the first piezoelectric element and the third piezoelectric element formed vertically symmetrically, and a set of piezoelectric elements composed of the second piezoelectric element and the fourth piezoelectric element. Is arranged.

The invention according to claim 5 of the present application is characterized in that, in the piezoelectric element according to any one of claims 1 to 4, the piezoelectric film is a film that vibrates due to acoustic pressure.

In the piezoelectric element of the present invention, the piezoelectric element formed on the first piezoelectric film and the piezoelectric element formed on the second piezoelectric film are arranged so as to overlap vertically symmetrically, so that the residual stress and temperature fluctuation of the overlapping piezoelectric films After canceling each other out the piezoelectric voltage generated due to the above to reduce the influence of the residual stress of the piezoelectric film, the piezoelectric voltage generated by the first piezoelectric film and the piezoelectric voltage generated by the second piezoelectric film are combined. It is possible to raise the level of the output signal by superimposing it.

In particular, in the present invention, the piezoelectric voltage is superimposed and the level of the output signal can be raised by connecting a plurality of sets of piezoelectric elements in which a plurality of piezoelectric elements are connected.

Further, according to the present invention, when the piezoelectric film is curved and deformed by vibration, the piezoelectric element formed on the first piezoelectric film and the piezoelectric formed on the second piezoelectric film are formed for each region defined by the bending point of the displacement. By arranging the pair with the element, the piezoelectric element is separated into the tensile stress region and the compressive stress region generated in the stretching direction of the piezoelectric film for each partitioned region, and the voltage signals generated in each region are superimposed. It is possible to connect them so that they can be efficiently converted into electrical energy and taken out.

According to the present invention, the connection between the piezoelectric elements can be performed by extending the electrodes of the piezoelectric elements, and electricity is efficiently applied in that a connecting means such as a through hole that affects the displacement of the piezoelectric film is not required. It has the advantage of being able to be converted into energy.

In particular, when the piezoelectric film of the piezoelectric element of the present invention is set to a thickness that vibrates due to acoustic pressure and is used as an acoustic transducer, high sensitivity and improvement in the signal-to-noise ratio are expected.

It is a top view of the electrode of the piezoelectric element of the 1st Example of this invention. It is a partial cross-sectional view of the piezoelectric element of the 1st Example of this invention. It is explanatory drawing of 1st Example of this invention. It is explanatory drawing of 1st Example of this invention. It is a partial cross-sectional view of the piezoelectric element of the 2nd Example of this invention. It is explanatory drawing of the conventional piezoelectric element.

The piezoelectric element of the present invention has a structure in which the periphery of the piezoelectric film (the outer peripheral portion of the diaphragm) is fixed to the support substrate. The piezoelectric film has a laminated structure including at least two layers of piezoelectric films. Each piezoelectric film is formed with a plurality of piezoelectric elements in which electrodes are arranged so as to sandwich a part thereof, and each piezoelectric element is connected in parallel or in series. In particular, in the present invention, the piezoelectric elements are arranged so as to be vertically symmetrically overlapped with each other. By adopting the above configuration, the present invention aims to improve the signal-to-noise ratio by mutually canceling the piezoelectric voltage generated by the residual stress and the temperature fluctuation due to the output of the piezoelectric elements overlapping vertically. Further, by arranging a set of piezoelectric elements that are vertically symmetrically overlapped at a predetermined position, a signal can be efficiently extracted. Further, in the present invention, a set of piezoelectric elements is connected in series. Hereinafter, a case where the piezoelectric element of the present invention is configured as an acoustic transducer will be described in detail as an example.

A first embodiment of the present invention will be described. FIG. 1 schematically shows a plan view of the electrodes of the piezoelectric element of the first embodiment, and FIG. 2 schematically shows a cross-sectional view of the piezoelectric elements A and B on which the electrodes of the piezoelectric element shown in FIG. 1 are arranged. ing. As shown in FIG. 1A, the lower layer electrode is composed of a plurality of electrodes 4a1 to 4a4, and has a structure in which two adjacent electrodes are connected to each other. For example, the electrode 4a1 has a structure in which two electrode portions constituting the two piezoelectric elements and an extension portion for connecting the electrode portions are integrated. Similarly, as shown in FIG. 1B, the intermediate layer electrode is also composed of a plurality of electrodes 4b1 to 4b5, and the electrodes 4b1 to 4b4 have a structure in which two adjacent electrodes are connected via an extension portion, and the electrodes 4b5. Has an independent structure. The upper layer electrodes 4c1 to 4c4 have the same shape as the lower layer electrodes.

FIG. 2 shows a cross-sectional view of a plane A and a plane B in which a lower layer electrode, an intermediate layer electrode, and an upper layer electrode of the piezoelectric element shown in FIG. 1 are laminated with a piezoelectric film interposed therebetween. As shown in FIG. 2, piezoelectric films 3a and 3b are laminated and formed on a silicon substrate 1 serving as a support substrate via an insulating film 2 made of a silicon oxide film (SiO ₂ ). The periphery of the piezoelectric films 3a and 3b is fixed to the silicon substrate 1 via the insulating film 2, and constitutes, for example, a circular diaphragm. As the piezoelectric film, for example, aluminum nitride (AlN) can be used, and the crystal orientation directions exhibiting piezoelectricity are formed so as to be the same direction in each of the piezoelectric thin films formed in a laminated manner. A vent hole is formed in the central portion.

Explaining the structure of the piezoelectric element of this embodiment in detail, electrodes 4a1, electrodes 4a2, electrodes 4a3, and electrodes 4a4, which are lower layer electrodes, are formed on the back surface side of the piezoelectric film 3a. Further, electrodes 4b1, electrodes 4b2, electrodes 4b3, electrodes 4b4, and electrodes 4b5, which are intermediate layer electrodes, are formed on the upper surface side of the piezoelectric film 3a and the lower surface side (corresponding to the space between the films) of the piezoelectric film 3b. 4b1 is connected to the wiring electrode 5a, and the electrode 4b5 is connected to the wiring electrode 5b. Further, electrodes 4c1, electrodes 4c2, electrodes 4c3, and electrodes 4c4, which are upper layer electrodes, are formed on the upper surface side of the piezoelectric film 3b. These electrodes are arranged in a circle as shown in FIGS. 1A and 1B. The electrode can be formed of a metal thin film such as molybdenum (Mo), platinum (Pt), titanium (Ti), iridium (Ir), and ruthenium (Ru).

With this configuration, as shown in the cross-sectional view in FIG. 2, the piezoelectric element C1 (corresponding to the first piezoelectric element) in the region where the electrode 4a1, the piezoelectric film 3a (corresponding to the first piezoelectric film) and the electrode 4b1 overlap each other. Is formed. Similarly, in the region where the electrode 4a1, the piezoelectric film 3a and the electrode 4b2 overlap, the piezoelectric element C2 (corresponding to the second piezoelectric element), the electrode 4c1, the piezoelectric film 3b (corresponding to the second piezoelectric film) and the region where the electrode 4b1 overlap. In the piezoelectric element C3 (corresponding to the third piezoelectric element), the piezoelectric element C4 (corresponding to the fourth piezoelectric element) is formed in the region where the electrode 4c1, the piezoelectric film 3b and the electrode 4b2 overlap.

Similarly, the piezoelectric element C5 (corresponding to the piezoelectric element C1 in FIG. 2) is formed in the region where the electrodes 4a2, the piezoelectric film 3a and the electrode 4b2 overlap, and the piezoelectric element C6 (corresponds to the piezoelectric element C1 in FIG. 2) is formed in the region where the electrodes 4a2, the piezoelectric film 3a and the electrode 4b3 overlap. Similarly, the piezoelectric element C7 (corresponding to the piezoelectric element C3) is in the region where the piezoelectric element C2), the electrode 4c2, the piezoelectric film 3b and the electrode 4b2 overlap, and the piezoelectric element C8 is in the region where the electrode 4c2, the piezoelectric film 3b and the electrode 4b3 overlap. (Corresponding to the piezoelectric element C4) is formed.

Further, the piezoelectric element C9 (corresponding to the piezoelectric element C1 in FIG. 2) is formed in the region where the electrodes 4a3, the piezoelectric film 3a and the electrode 4b3 overlap, and the piezoelectric element C10 (piezoelectric) is formed in the region where the electrodes 4a3, the piezoelectric film 3a and the electrode 4b4 overlap. Piezoelectric element C11 (corresponding to piezoelectric element C3) in the region where the element C2), electrode 4c3, piezoelectric film 3b and electrode 4b3 overlap, and piezoelectric element C12 (piezoelectric element) in the region where the electrode 4c3, piezoelectric film 3b and electrode 4b4 overlap. Corresponds to C4) is formed.

Further, the piezoelectric element C13 (corresponding to the piezoelectric element C1 in FIG. 2) is formed in the region where the electrodes 4a4, the piezoelectric film 3a and the electrode 4b4 overlap, and the piezoelectric element C14 (piezoelectric) is formed in the region where the electrodes 4a4, the piezoelectric film 3a and the electrode 4b5 overlap. Piezoelectric element C15 (corresponding to piezoelectric element C3) in the region where the element C2), electrode 4c4, piezoelectric film 3b and electrode 4b4 overlap, and piezoelectric element C16 (piezoelectric element C16) in the region where the electrode 4c4, piezoelectric film 3b and electrode 4b5 overlap. Corresponds to C4) is formed.

Here, for example, the first piezoelectric element C1 and the second piezoelectric element C2 use the electrodes 4a1 constituting the piezoelectric element in common, so that the electrodes 4a1 do not overlap with the opposing electrodes (electrodes 4b1 and electrodes 4b2, respectively). It is connected by the area (corresponding to the extension). Similarly, the third piezoelectric element C3 and the fourth piezoelectric element C4 commonly use the electrodes 4c1 constituting the piezoelectric element, so that the electrodes 4b1 do not overlap with the opposing electrodes (electrodes 4b1 and electrodes 4b2, respectively). It is connected by an area (corresponding to an extension). With such a connection, it is not necessary to form a connecting means that affects the displacement of the piezoelectric element such as a through hole in the piezoelectric film.

As a result, the series connection of the first piezoelectric element C1 and the second piezoelectric element C2 and the series connection of the third piezoelectric element C3 and the fourth piezoelectric element C4 are connected in parallel. In this embodiment, four sets of piezoelectric elements corresponding to the first to fourth piezoelectric elements are connected in series, and these piezoelectric elements C1 to C16 are inserted between the wiring electrode 5a and the wiring metal 5b. It becomes a connected configuration. Specifically, it has the configuration shown in FIG. In FIG. 3, the first piezoelectric element C1 and the third piezoelectric element C3 are arranged on the outer peripheral side of the piezoelectric film, that is, the piezoelectric film on the fixed portion side fixed to the support substrate, and the second piezoelectric element C2, The fourth piezoelectric element C4 is arranged on the central side of the piezoelectric film, that is, on the piezoelectric film between the region where the first piezoelectric element C1 and the third piezoelectric element C3 are formed and the center of the piezoelectric film. Similarly, the piezoelectric elements C5, C7, C9, C11, C13 and C15 are arranged on the fixed portion side of the piezoelectric film, and the piezoelectric elements C6, C8, C10, C12, C14 and C16 are arranged on the center side of the piezoelectric film. ..

Further, as is clear from FIG. 2, the first piezoelectric element C1 and the third piezoelectric element C3, and the second piezoelectric element C2 and the fourth piezoelectric element C4 are electrodes in at least a region so as to form each piezoelectric element. It is vertically symmetrical with respect to the surface passing through the center of the 4b1 and the electrode 4b2 in the thickness direction.

When the piezoelectric element of the present invention is configured as an acoustic transducer, acoustic pressure is applied from the pores 6 formed in the silicon substrate 1. The piezoelectric film that receives the acoustic pressure is curved and displaced upward. As a result, tensile stress and compressive stress are generated in the aluminum nitride constituting the piezoelectric film.

FIG. 4 shows an example in which an acoustic pressure signal is applied to the piezoelectric element in the region described in FIG. 2 and the piezoelectric film is displaced upward. As shown in FIG. 4, tensile stress and compressive stress are generated in the piezoelectric film, and the stress direction of the piezoelectric film is divided into two regions depending on the inflection point of displacement. Specifically, a tensile stress is generated in the piezoelectric film 3a and a compressive stress is generated in the piezoelectric film 3b at the outer peripheral portion near the fixed portion where the circular piezoelectric film is fixed to the silicon substrate 1 via the insulating film 2. Occur. On the other hand, in the central portion inside the piezoelectric film 3a, a compressive stress is generated, and a tensile stress is generated in the piezoelectric film 3b. In this way, it is divided into two regions where the stress direction differs depending on the inflection point of displacement.

By the way, in the piezoelectric element of this embodiment, as shown in FIG. 2, the piezoelectric element C1 and the piezoelectric element C2 are connected in series, and the piezoelectric element C3 and the piezoelectric element C4 are connected in series, and further up and down. It has a symmetric structure. Here, the voltage generated in the outer peripheral portion and the voltage generated in the central portion have opposite polarities and can be set to the same value, and it is possible to cancel out the in-phase voltage caused by the residual stress and the temperature fluctuation. It becomes.

Further, since the piezoelectric element of this embodiment has a structure in which four sets of piezoelectric elements composed of the piezoelectric elements C1 to C4 are connected in series, each of the four sets based on the application of an acoustic pressure signal. The output signal (voltage) of the set of piezoelectric elements is superimposed and added without including the signal due to residual stress or temperature fluctuation, and the ratio of the output voltage (V _out ) to the acoustic pressure (P _a ) (V _out / P _a). ), It is possible to increase the sensitivity as an acoustic transducer.

It is desirable that the size of each electrode is optimized from the viewpoint of maximizing the signal-to-noise ratio. This wiring electrodes 5a, the capacity of the equivalent capacitor as seen from 5b when the C _out, of the electrodes so as to maximize the energy stored in the equivalent capacitor ^{_{(C out · V out 2/}} 2) You just have to decide the size.

Specifically, a design example of the film thickness of each piezoelectric thin film and the size of the electrodes is shown. For example, the input signal is human voice, and the resonance frequency of the vibrating part is 20 kHz. In addition, the plane dimensions are set so that they can be mounted on electronic devices such as smartphones. The diameter of the vibrating plate is 800 μm, the thickness of the piezoelectric films 3a and 3b made of aluminum nitride is 0.37 μm, the thickness of the electrodes 4a1 to 4a4 made of molybdenum, the electrodes 4b1 to 4b5, and the thickness of the electrodes 4c1 to 4c4 are all 50 nm. The dimension of the electrode from the outer periphery of one electrode 4b1 of the first capacitor C1 toward the inside is 75 μm, and the dimension of the electrode toward the outside from the center of a part of the electrode 4b2 which is a small fan shape toward the inside. Is 230 μm.

In this way, the signal (capacity value) output from the pair of the first piezoelectric element C1 and the third piezoelectric element C3 and the signal (capacity) output from the pair of the second piezoelectric element C2 and the piezoelectric element C4. The values) are almost equal, and the same applies to the set of four piezoelectric elements corresponding to the set of piezoelectric elements consisting of the set of piezoelectric elements C1 to C4, so that the superimposed signal can be obtained, and the holes 6 It was confirmed that the sensitivity was about 10 mV / Pa when the capacity was set to 3 mm ³ .

Next, a second embodiment will be described. Generally, when a piezoelectric film such as aluminum nitride is deposited by a sputtering method, it is known that the surface (base) on which the piezoelectric film is deposited is affected. In the case of the piezoelectric element described in the first embodiment, when the piezoelectric film 3b is deposited, the portion where the electrode 4b1 or the like made of molybdenum is formed on the base surface and the electrode are not formed, and the piezoelectric film 3a is formed. There is a large exposed part. It is very difficult to form a piezoelectric film having uniform characteristics on such a base surface.

Therefore, the portion where the electrode is not formed may be coated with the same material as the electrode. Specifically, at the same time as the electrodes 4a1 to 4a4 to be the lower layer electrodes, a dummy electrode (an electrode including the electrode 4d1 shown in FIG. 5) that is not connected to these electrodes is formed in a region where these electrodes are not formed. Similarly, at the same time as the electrodes 4b1 to 4b5 to be the intermediate layer electrodes, a dummy electrode (an electrode including the electrode 4d2 shown in FIG. 5) that is not connected to these electrodes is formed in a region where these electrodes are not formed. The dummy electrode formed in this way makes it possible to form a piezoelectric film having uniform characteristics. At the same time as the electrodes 4c1 to 4c serving as the upper layer electrodes, it is also possible to form a region in which these electrodes are not formed and an electrode not connected to these electrodes (an electrode including the electrode 4d3 shown in FIG. 5). By forming this dummy electrode, it is possible to form a structure that is almost vertically symmetrical with respect to the surface passing through the center in the thickness direction of the intermediate layer electrode, and the stress of tension and compression is balanced and the stress becomes zero. The central axial plane is in the intermediate layer electrode plane, and the acoustic pressure can be efficiently taken out as an output voltage.

Although the examples of the present invention have been described above, it goes without saying that the present invention is not limited to the above examples. Specifically, the piezoelectric film is not limited to aluminum nitride, and scandium aluminum nitride (Al _1-x Sc _x N), zinc oxide (ZnO), and lead zirconate titanate (PZT) can also be used. It is possible. Further, the shape of each electrode, the number of piezoelectric elements to be connected, and the connection can be changed as appropriate.

1: Silicon substrate 2: Insulating film, 3a, 3b: Piezoelectric thin film, 4a, 4b, 4c, 4d: Electrode, 5a, 5b: Wiring electrode, 6: Vent

Claims (5)

In a piezoelectric element including a piezoelectric film whose circumference is fixed to a support substrate and a pair of electrodes arranged so as to sandwich the piezoelectric film.
The piezoelectric film has a laminated structure including at least a first piezoelectric film and a second piezoelectric film.
A plurality of sets of the pair of electrodes arranged so as to sandwich the first piezoelectric film are provided, and at least the first piezoelectric element and the second piezoelectric element are formed.
A plurality of sets of the pair of electrodes arranged so as to sandwich the second piezoelectric film are provided, and at least a third piezoelectric element and a fourth piezoelectric element are formed.
The first piezoelectric element and the third piezoelectric element are arranged on the fixed portion side of the piezoelectric film fixed to the support substrate, and the second piezoelectric element and the fourth piezoelectric element are arranged on the center side of the piezoelectric film. And that the piezoelectric element of
Wherein the first piezoelectric element the third piezoelectric element is connected in parallel, wherein the second piezoelectric element fourth piezoelectric elements are connected in parallel, before Symbol said second and first piezoelectric element The piezoelectric elements are connected in series, the third piezoelectric element and the fourth piezoelectric element are connected in series, and the first piezoelectric element and the third piezoelectric element are vertically symmetrically laminated. The piezoelectric element is characterized in that the second piezoelectric element and the fourth piezoelectric element are vertically symmetrically laminated. In the piezoelectric element according to claim 1,
A piezoelectric element, characterized in that a set of piezoelectric elements composed of the first to fourth piezoelectric elements is arranged in a plurality of regions defined by a dividing line passing through the center of the piezoelectric film. In the piezoelectric element according to any one of claims 1 or 2.
The set of piezoelectric elements connected in parallel is connected by an extension portion continuous from the electrode of the piezoelectric element arranged on the front surface, the back surface, or between the first piezoelectric film or the second piezoelectric film. A piezoelectric element characterized by this. In the piezoelectric element according to any one of claims 1 to 3,
When the piezoelectric film is curved and displaced due to vibration, the first piezoelectric element and the third piezoelectric element are formed by stacking at least vertically symmetrically for each region defined by the bending point of the displacement. A piezoelectric element characterized in that any one of a set of piezoelectric elements and a set of piezoelectric elements including the second piezoelectric element and the fourth piezoelectric element is arranged. In the piezoelectric element according to any one of claims 1 to 4,
The piezoelectric film is a piezoelectric element that vibrates due to acoustic pressure.

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