WO2021053892A1 - Piezoelectric device and method for manufacturing same - Google Patents

Abstract

Provided is a piezoelectric device (100) in which a membrane part (120) is indirectly supported by a base part (110), is located on the upper side relative to the base part (110), and is formed of a plurality of layers (130). The membrane part (120) does not overlap with the base part (110). The membrane part (120) includes a single crystal piezoelectric layer (140), an upper electrode layer (150), and a lower electrode layer (160). The upper electrode layer (150) is disposed on the upper side of the single crystal piezoelectric layer (140). The lower electrode layer (160) is disposed so as to face at least part of the upper electrode layer (150) with the single crystal piezoelectric layer (140) interposed therebetween. The membrane part (120) is provided with a through-groove (121) vertically penetrating therethrough. A first cross-section (141) of the single crystal piezoelectric layer (140) facing the through-groove (121) is covered by a first protection part (190) which is located with the through-groove (121) sandwiched therebetween.

Description

Piezoelectric device and its manufacturing method

The present invention relates to a piezoelectric device and a method for manufacturing the same.

International Publication No. 2017/218299 (Patent Document 1) is a document that discloses the configuration of the piezoelectric device. The piezoelectric device described in Patent Document 1 includes a substrate and a membrane portion. The substrate has an opening formed to penetrate. The membrane portion is formed of at least one elastic layer and at least one piezoelectric layer sandwiched between the upper electrode layer and the lower electrode layer. The membrane portion is attached to the substrate above the opening. In the membrane portion, a through groove is formed by etching.

International Publication No. 2017/218299

The piezoelectric layer is exposed in the through groove of the membrane portion. In the cross section forming the through groove, the surface of the piezoelectric layer may be roughened, and the electrical characteristics of the piezoelectric device may be deteriorated. Therefore, there is room for improving the environmental resistance of the piezoelectric device by protecting the cross section forming the through groove of the piezoelectric layer.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a piezoelectric device capable of improving environmental resistance.

The piezoelectric device based on the present invention includes a base portion and a membrane portion. The membrane portion is indirectly supported by the base portion, is located above the base portion, and is composed of a plurality of layers. The membrane portion does not overlap the base portion. The membrane portion includes a single crystal piezoelectric layer, an upper electrode layer, and a lower electrode layer. The upper electrode layer is arranged above the single crystal piezoelectric layer. The lower electrode layer is arranged so as to face at least a part of the upper electrode layer via the single crystal piezoelectric layer. The membrane portion is provided with a through groove that penetrates in the vertical direction. The first cross section of the single crystal piezoelectric layer facing the through groove is covered with a first protective portion located with the through groove in between.

The method for manufacturing a piezoelectric device based on the present invention includes a step of arranging a lower electrode layer below the single crystal piezoelectric layer and a step of forming a groove for a first protective portion penetrating in the vertical direction in the single crystal piezoelectric layer. A step of filling the groove for the first protective portion with the first protective portion, a step of forming a first laminated body including at least a single crystal piezoelectric layer, and a second laminated body under the first laminated body. The step of joining, the step of adjusting the thickness of the single crystal piezoelectric layer, and the upper electrode layer on the upper side of the single crystal piezoelectric layer, at least a part of which faces the lower electrode layer via the single crystal piezoelectric layer. It is provided with a step of arranging the above, a step of forming a through groove, and a step of forming a recess. In the step of forming the through groove, a through groove that penetrates at least the first laminated body in the vertical direction is formed so as to divide the first protective portion. In the step of forming the recess, when viewed from above and below, the upper electrode layer and the lower electrode layer overlap with each other via the single crystal piezoelectric layer and the portion where the through groove is located. As described above, a recess is formed which is opened on the lower side of the second laminated body and communicates with the through groove.

According to the present invention, the environmental resistance of the piezoelectric device can be improved.

It is a top view of the piezoelectric device which concerns on Embodiment 1 of this invention. FIG. 5 is a cross-sectional view of the piezoelectric device of FIG. 1 as viewed from the direction of the arrow along line II-II. It is sectional drawing which shows the state which provided the lower electrode layer on the lower surface of the single crystal piezoelectric layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the state which formed the groove for the 1st protection part in the single crystal piezoelectric layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the state which provided the lower surface of each of the single crystal piezoelectric layer and the lower electrode layer, and the intermediate layer in the groove for the 1st protection part in the manufacturing method of the piezoelectric device which concerns on Embodiment 1 of this invention. .. FIG. 5 is a cross-sectional view showing a state in which the lower surface of the intermediate layer is scraped in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention. It is sectional drawing which shows the state which prepared the 2nd laminated body in the manufacturing method of the piezoelectric device which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the state which the 2nd laminated body is bonded to the lower surface of the intermediate layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the state which the 2nd laminated body was bonded to the lower surface of the intermediate layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the state which the upper surface of each of the single crystal piezoelectric layer and the 1st protection part was shaved in the manufacturing method of the piezoelectric device which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the state which provided the upper electrode layer on the upper surface of the single crystal piezoelectric layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the state which formed the through groove from the 1st protection part to the semiconductor layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 1 of this invention. FIG. 5 is a cross-sectional view showing a state in which a groove is formed in a single crystal piezoelectric layer in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention. FIG. 5 is a cross-sectional view showing a state in which a first external electrode is provided on an upper electrode layer and a second external electrode is provided on a lower electrode layer in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention. It is sectional drawing of the piezoelectric device which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the state which formed the groove for the 1st protection part and the groove for the 2nd protection part in the single crystal piezoelectric layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 2 of this invention. In the method for manufacturing a piezoelectric device according to the second embodiment of the present invention, a first intermediate layer is provided on the lower surface of each of the single crystal piezoelectric layers, in the groove for the first protective portion, and in the groove for the second protective portion. It is sectional drawing which shows the state. It is sectional drawing which shows the state which the lower surface of the 1st intermediate layer was shaved in the manufacturing method of the piezoelectric device which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the state which provided the lower electrode layer on the lower surface of the 1st intermediate layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the state which provided the 2nd intermediate layer on the lower surface of each of the 1st intermediate layer and the lower electrode layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the state which the lower surface of the 2nd intermediate layer was shaved in the manufacturing method of the piezoelectric device which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the state which the 2nd laminated body is bonded to the lower surface of the 2nd intermediate layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the state which the 2nd laminated body was bonded to the lower surface of the 2nd intermediate layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the state which the upper surface of each of the single crystal piezoelectric layer, the 1st protection part and the 2nd protection part was cut in the manufacturing method of the piezoelectric device which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the state which provided the upper electrode layer on the upper surface of the single crystal piezoelectric layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the state which formed the through groove from the 1st protection part to the semiconductor layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the state which formed the groove part from the 2nd protection part to the 1st intermediate layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the state which provided the 1st external electrode on the upper electrode layer, and provided the 2nd external electrode on the lower electrode layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 2 of this invention. It is sectional drawing of the piezoelectric device which concerns on Embodiment 3 of this invention. It is sectional drawing which shows the state which the 1st intermediate layer was cut from the lower side in the manufacturing method of the piezoelectric device which concerns on Embodiment 3 of this invention. It is sectional drawing which shows the state which provided the lower electrode layer on the lower surface of the single crystal piezoelectric layer and the 2nd protection part in the manufacturing method of the piezoelectric device which concerns on Embodiment 3 of this invention. It is sectional drawing which shows the state which provided the 2nd intermediate layer on the lower surface of each of the 1st protection part and the single crystal piezoelectric layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 3 of this invention. It is sectional drawing of the piezoelectric device which concerns on Embodiment 4 of this invention. It is sectional drawing which shows the state which the 2nd laminated body is bonded to the lower surface of the 1st intermediate layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 4 of this invention. It is sectional drawing which shows the state which the 2nd laminated body was bonded to the lower surface of the 1st intermediate layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 4 of this invention. It is sectional drawing which shows the state which the upper surface of each of the single crystal piezoelectric layer, the 1st protection part and the 2nd protection part was cut in the manufacturing method of the piezoelectric device which concerns on Embodiment 4 of this invention. It is sectional drawing which shows the state which provided the upper electrode layer on the upper surface of the single crystal piezoelectric layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 4 of this invention. It is sectional drawing which shows the state which formed the through groove from the 1st protection part to the semiconductor layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 4 of this invention. It is sectional drawing which shows the state which formed the groove part from the 2nd protection part to the semiconductor layer in the manufacturing method of the piezoelectric device which concerns on Embodiment 4 of this invention. FIG. 5 is a cross-sectional view showing a state in which a first external electrode is provided on an upper electrode layer and a second external electrode is provided on a semiconductor layer which is a lower electrode layer in the method for manufacturing a piezoelectric device according to the fourth embodiment of the present invention. ..

Hereinafter, the piezoelectric device according to each embodiment of the present invention will be described with reference to the drawings. In the following description of the embodiment, the same or corresponding parts in the drawings are designated by the same reference numerals, and the description thereof will not be repeated. Also, in the following description, when referring to the concept of up or down, it does not necessarily mean absolute up or down, but rather relative up or down in the illustrated posture. There is.

(Embodiment 1)
FIG. 1 is a plan view of the piezoelectric device according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view of the piezoelectric device of FIG. 1 as viewed from the direction of the arrow along line II-II.

As shown in FIGS. 1 and 2, the piezoelectric device 100 according to the first embodiment of the present invention includes a base portion 110 and a membrane portion 120.

As shown in FIG. 2, in the present embodiment, the base 110 includes a lower base 110a and an upper base 110b located above the lower base 110a. The base 110 has an upper main surface 111 and a lower main surface 112 located on the opposite side of the upper main surface 111. In the present embodiment, the upper surface of the upper base 110b is the upper main surface 111, and the lower surface of the lower base 110a is the lower main surface 112. The base 110 is formed with a recess 113 that penetrates the lower base 110a and the upper base 110b in the vertical direction.

The material constituting the base 110 is not particularly limited. In this embodiment, the lower base 110a is made of Si. The upper base 110b is made of SiO ₂ .

A plurality of layers 130 are laminated on the upper main surface 111 of the base 110. The membrane portion 120 is a portion of the plurality of layers located above the recess 113. That is, the membrane portion 120 is composed of a plurality of layers 130. The plurality of layers 130 extend from the membrane portion 120 to the upper side of the base portion 110.

Since the membrane portion 120 is located above the recess 113 of the base 110, it does not overlap the base 110. That is, the membrane portion 120 is indirectly supported by the base portion 110 and is located above the base portion 110.

The membrane portion 120 is provided with a through groove 121 penetrating in the vertical direction. In the present embodiment, the width of the through groove 121 is substantially constant from the upper end to the lower end. The width of the through groove 121 is preferably 10 μm or less.

In the present embodiment, the membrane portion 120 includes a single crystal piezoelectric layer 140, an upper electrode layer 150, a lower electrode layer 160, an intermediate layer 170, a semiconductor layer 180, and a first protective portion 190. .. That is, the plurality of layers 130 constituting the membrane portion 120 include the single crystal piezoelectric layer 140, the upper electrode layer 150, the lower electrode layer 160, the intermediate layer 170, the semiconductor layer 180, and the first protective portion 190. have.

The single crystal piezoelectric layer 140 is located above the base 110. The single crystal piezoelectric layer 140 has a first cross section 141 and a second cross section 142. The distance between the first cross sections 141 increases from the upper electrode layer 150 side to the lower electrode layer 160 side. The distance between the second cross sections 142 is substantially constant from the upper electrode layer 150 side to the lower electrode layer 160 side.

In the present embodiment, the single crystal piezoelectric layer 140 is formed with a groove portion 143 that penetrates the single crystal piezoelectric layer 140 in the vertical direction. The second cross section 142 faces the groove portion 143.

The thickness of the single crystal piezoelectric layer 140 is, for example, 5 μm or less. The single crystal piezoelectric layer 140 is made of lithium tantalate or lithium niobate. The single crystal piezoelectric layer 140 composed of lithium tantalate or lithium niobate has a uniform polarization state, and the direction parallel to the plane on the base 110 side of the single crystal piezoelectric layer 140 is the in-plane direction. In addition, it has the property of being easy to cleave while forming a cleavage plane in a specific in-plane direction and out-of-plane direction.

The upper electrode layer 150 is arranged above the single crystal piezoelectric layer 140. An adhesion layer may be arranged between the upper electrode layer 150 and the single crystal piezoelectric layer 140.

The lower electrode layer 160 is arranged in the membrane portion 120 so as to face at least a part of the upper electrode layer 150 via the single crystal piezoelectric layer 140. In the present embodiment, the lower electrode layer 160 is arranged below the single crystal piezoelectric layer 140. An adhesion layer may be arranged between the lower electrode layer 160 and the single crystal piezoelectric layer 140.

In the present embodiment, the lower electrode layer 160 has an etching stop layer 161. The etching stop layer 161 is located at a portion of the lower electrode layer 160 on the base 110 side. The etching stop layer 161 may be located at a portion of the lower electrode layer 160 opposite to the base 110 side.

The lower electrode layer 160 is arranged above the base 110 and below the groove 143 formed in the single crystal piezoelectric layer 140. The lower electrode layer 160 is located so as to cover the lower part of the groove portion 143. In the present embodiment, the etching stop layer 161 of the lower electrode layer 160 is located so as to cover the lower part of the groove portion 143.

Although a plurality of cross sections of the upper electrode layer 150 are shown in FIG. 2, the upper electrode layer 150 is continuously formed on the upper side of the single crystal piezoelectric layer 140 when viewed from above and below. ing. The lower electrode layer 160 is also continuously formed under the single crystal piezoelectric layer 140 when viewed from above and below.

In the present embodiment, when viewed from the vertical direction, the outer edges of the upper electrode layer 150 and the lower electrode layer 160 are preferably located non-parallel to the cleavage direction of the single crystal piezoelectric layer 140. .. Further, when the piezoelectric device 100 according to the present embodiment includes a semiconductor layer made of Si, the outer edges of the upper electrode layer 150 and the lower electrode layer 160 are set with respect to the opening direction of the semiconductor layer. It is preferable that they are located non-parallel.

In the present embodiment, each of the upper electrode layer 150 and the lower electrode layer 160 is made of a conductive material such as Pt, Ni, or Au. The etching stop layer 161 is preferably a material that has conductivity and is not etched when the single crystal piezoelectric 140 layer is etched. It is composed of an etching stop layer 161 such as Ni. The material of the adhesion layer is not particularly limited as long as it is a material having conductivity and adhesion. The adhesion layer is composed of, for example, a Ti, Cr, Ni or NiCr alloy. When the single crystal piezoelectric layer 140 is made of lithium niobate, the adhesion layer is preferably made of a NiCr alloy that is less likely to diffuse atoms into the single crystal piezoelectric layer 140 as compared with Ti.

The piezoelectric device 100 according to the present embodiment further includes a first external electrode 155 and a second external electrode 165. The first external electrode 155 is electrically connected to the upper electrode layer 150, and specifically, is arranged on the upper electrode layer 150 above the base 110. The second external electrode 165 is electrically connected to the lower electrode layer 160. In the present embodiment, the second external electrode 165 is provided on the lower electrode layer 160, on the second cross section 142 which is the inner side surface of the groove portion 143, and on the upper surface of the single crystal piezoelectric layer 140. The material constituting each of the first external electrode 155 and the second external electrode 165 is not particularly limited as long as it is a conductive material such as metal.

The intermediate layer 170 is arranged below the single crystal piezoelectric layer 140. In the present embodiment, the intermediate layer 170 includes the lower surface of the lower electrode layer 160, the lower surface of the single crystal piezoelectric layer 140 that is not covered by the lower electrode layer 160, and the lower surface of the first protective portion 190. It is provided so that it touches. The intermediate layer 170 is composed of a dielectric layer such as _{SiO 2.}

The semiconductor layer 180 is arranged below the intermediate layer 170. The semiconductor layer 180 is provided so as to be in contact with the lower surface of the intermediate layer 170. The semiconductor layer 180 may be provided on the lower surface of the intermediate layer 170 via the metal layer. In the present embodiment, in the membrane portion 120, the lower surface of the semiconductor layer 180 is exposed in the recess 113. The semiconductor layer 180 is made of, for example, Si.

The first protection unit 190 is located on the first cross section 141. The first protective portion 190 is provided with a through groove 121. That is, the first cross section 141 of the single crystal piezoelectric layer 140 facing the through groove 121 is covered with the first protective portion 190 located with the through groove 121 in between.

In the present embodiment, the first protection unit 190 is composed of a member integrated with the intermediate layer 170. That is, the lower surface of the first protective portion 190 is connected to the intermediate layer 170. With the above configuration, the first protective portion 190 and the intermediate layer 170 can be laminated at the same time, and the manufacturing process of the piezoelectric device 100 can be simplified. Further, when the first protective portion 190 is made of the same material as the material constituting the intermediate layer 170, it is possible to suppress the formation of a crystal boundary between the lower surface of the first protective portion 190 and the intermediate layer 170. .. Therefore, it is possible to suppress the occurrence of cracks from the crystal boundary. The first protection unit 190 is made of a dielectric material such as _{SiO 2.}

With the above configuration, in the piezoelectric device 100 according to the present embodiment, the single crystal piezoelectric layer 140 expands and contracts when a voltage is applied between the upper electrode layer 150 and the lower electrode layer 160. On the other hand, in the membrane portion 120, the members other than the single crystal piezoelectric layer 140 are not deformed by the application of voltage. Therefore, the membrane portion 120 bends and vibrates up and down in response to the expansion and contraction of the single crystal piezoelectric layer 140 due to the application of the voltage.

Hereinafter, a method for manufacturing the piezoelectric device according to the first embodiment of the present invention will be described.
FIG. 3 is a cross-sectional view showing a state in which a lower electrode layer is provided on the lower surface of the single crystal piezoelectric layer in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention. As shown in FIG. 3, the lower electrode layer 160 is arranged below the single crystal piezoelectric layer 140. At this time, the thickness of the single crystal piezoelectric layer 140 is, for example, 200 μm or more and 500 μm or less. In the present embodiment, the lower electrode layer 160 is provided on the lower surface of the single crystal piezoelectric layer 140 by a lift-off method, a plating method, an etching method, or the like. More specifically, after providing the portion of the lower electrode layer 160 other than the etching stop layer 161, the etching stop layer 161 is provided. After the etching stop layer 161 is provided, a portion of the lower electrode layer 160 other than the etching stop layer 161 may be provided.

The lower electrode layer 160 is preferably provided by epitaxial growth. As a result, the fatigue characteristics of the membrane portion 120 due to the driving of the single crystal piezoelectric layer 140 are improved.

FIG. 4 is a cross-sectional view showing a state in which a groove for a first protective portion is formed in a single crystal piezoelectric layer in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention. As shown in FIG. 4, a groove 141A for the first protective portion is formed on the lower surface of the single crystal piezoelectric layer 140 from the lower side of the single crystal piezoelectric layer 140 by an etching method or the like. The depth of the groove 141A for the first protective portion may be, for example, about 10 μm.

FIG. 5 shows a state in which the lower surfaces of the single crystal piezoelectric layer and the lower electrode layer and the intermediate layer are provided in the groove for the first protective portion in the method for manufacturing the piezoelectric device according to the first embodiment of the present invention. It is a sectional view. As shown in FIGS. 4 and 5, each of the lower electrode layer 160 and the single crystal piezoelectric layer 140 in the groove 141A for the first protective portion by the CVD (Chemical Vapor Deposition) method or the PVD (Physical Vapor Deposition) method or the like. An intermediate layer 170 is provided on the lower surface of the. At this time, the intermediate layer 170 is provided so as to fill the inside of the groove 141A for the first protective portion.

FIG. 6 is a cross-sectional view showing a state in which the lower surface of the intermediate layer is scraped in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention. As shown in FIG. 6, the lower surface of the intermediate layer 170 is flattened by chemical mechanical polishing (CMP) or the like. In this way, the groove 141A for the first protective portion is filled with the first protective portion 190 made of the same member as the intermediate layer 170.

In the present embodiment, the first laminated body 10 including at least the single crystal piezoelectric layer 140 is formed by the above steps. Specifically, the first laminated body 10 in the present embodiment further includes a lower electrode layer 160, an intermediate layer 170, and a first protective portion 190.

FIG. 7 is a cross-sectional view showing a state in which a second laminated body is prepared in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention. FIG. 8 is a cross-sectional view showing a state in which the second laminated body is bonded to the lower surface of the intermediate layer in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention. FIG. 9 is a cross-sectional view showing a state in which the second laminated body is bonded to the lower surface of the intermediate layer in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention.

As shown in FIGS. 7 to 9, the second laminated body 20 is joined to the lower side of the first laminated body 10. The second laminated body 20 is composed of a base portion 110 in which the recess 113 is not formed, and a semiconductor layer 180 joined on the upper main surface 111 of the base portion 110. In the present embodiment, the second laminated body 20 is an SOI (Silicon on Insulator) substrate.

FIG. 10 is a cross-sectional view showing a state in which the upper surfaces of the single crystal piezoelectric layer and the first protective portion are scraped in the method for manufacturing the piezoelectric device according to the first embodiment of the present invention. As shown in FIG. 10, the thickness of the single crystal piezoelectric layer 140 is adjusted. Specifically, the upper surfaces of the single crystal piezoelectric layer 140 and the first protective portion 190 are each scraped by CMP or the like to make the single crystal piezoelectric layer 140 a desired thickness, and the first protective portion 190 is exposed. Let me. In this case, the thickness of the single crystal piezoelectric layer 140 is adjusted so that a desired amount of expansion and contraction of the single crystal piezoelectric layer 140 can be obtained by applying a voltage.

A release layer may be formed by implanting ions in advance on the upper surface side of the single crystal piezoelectric layer 140. In this case, the thickness of the single crystal piezoelectric layer 140 can be easily adjusted by peeling the peeling layer before the upper surface of the single crystal piezoelectric layer 140 is scraped by CMP or the like. The peeling layer may be scraped by CMP or the like.

FIG. 11 is a cross-sectional view showing a state in which an upper electrode layer is provided on the upper surface of the single crystal piezoelectric layer in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention. As shown in FIG. 11, a lower electrode is formed on the upper side of the single crystal piezoelectric layer 140 by a lift-off method (photolithography method), a plating method, an etching method, or the like, at least partially via the single crystal piezoelectric layer 140. The upper electrode layer 150 is arranged so as to face the layer 160. In the present embodiment, the upper electrode layer 150 is patterned by the lift-off method (photolithography method).

The upper electrode layer 150 is preferably provided by epitaxial growth. As a result, the fatigue characteristics of the membrane portion 120 due to the driving of the single crystal piezoelectric layer 140 are improved.

FIG. 12 is a cross-sectional view showing a state in which a through groove is formed from the first protective portion to the semiconductor layer in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention. As shown in FIG. 12, a through groove 121 is formed in the first protective portion 190 by etching from the upper side. Specifically, a through groove 121 that penetrates at least the first laminated body 10 in the vertical direction is formed so as to divide the first protective portion 190. In the present embodiment, the through groove 121 is formed so as to further penetrate the semiconductor layer 180. The through groove 121 may be formed so as to be located below the lower surface of the semiconductor layer 180.

FIG. 13 is a cross-sectional view showing a state in which a groove is formed in the single crystal piezoelectric layer in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention. As shown in FIG. 13, the groove portion 143 is formed by etching the single crystal piezoelectric layer 140 above the base portion 110. At this time, as shown in FIG. 13, the upper portion of the etching stop layer 161 of the lower electrode layer 160 may be etched.

FIG. 14 is a cross-sectional view showing a state in which the first external electrode is provided on the upper electrode layer and the second external electrode is provided on the lower electrode layer in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention. .. As shown in FIG. 14, a first external electrode 155 is provided on the upper electrode layer 150 and a second external electrode 165 is provided on the lower electrode layer 160 by a lift-off method, a plating method, an etching method, or the like. In the present embodiment, the second external electrode 165 is provided on the etching stop layer 161 of the lower electrode layer 160.

Finally, as shown in FIGS. 14 and 2, the recess 113 is formed. Specifically, when viewed from the vertical direction, the upper electrode layer 150 and the lower electrode layer 160 face each other via the single crystal piezoelectric layer 140, and the portion where the through groove 121 is located. A recess 113 that opens to the lower side of the second laminated body 20 and communicates with the through groove 121 is formed so as to overlap each other. In the present embodiment, the second laminated body 20 is subjected to deep reactive ion etching (Deep Reactive Ion Etching) to form a recess 113 in the base 110.

By the above steps, the piezoelectric device 100 according to the first embodiment of the present invention as shown in FIG. 2 is manufactured.

As described above, in the piezoelectric device 100 according to the first embodiment of the present invention, the membrane portion 120 is provided with a through groove 121 penetrating in the vertical direction. The first cross section 141 of the single crystal piezoelectric layer 140 facing the through groove 121 is covered with a first protective portion 190 located with the through groove 121 in between. Thereby, the environmental resistance of the piezoelectric device 100 can be improved.

In the present embodiment, the distance between the first cross sections 141 increases from the upper electrode layer 150 side to the lower electrode layer 160 side.

As a result, as compared with the case where the distance between the first cross sections is constant, the first protective portion 190 having good covering property can be obtained by laminating the first protective portion 190 from the lower side of the single crystal piezoelectric layer 140. Can be provided. As a result, in the single crystal piezoelectric layer 140, the internal stress caused by the first protective portion 190 is relaxed, so that cracks are less likely to occur and the reliability of the piezoelectric device 100 is improved.

The method for manufacturing the piezoelectric device 100 according to the first embodiment of the present invention includes a step of arranging the lower electrode layer 160 below the single crystal piezoelectric layer 140 and a first method of penetrating the single crystal piezoelectric layer 140 in the vertical direction. A step of forming the groove 141A for the protective portion, a step of filling the groove 141A for the first protective portion with the first protective portion 190, a step of forming the first laminated body 10 including at least the single crystal piezoelectric layer 140, and the first step. A step of joining the second laminated body 20 to the lower side of the 1 laminated body 10, a step of adjusting the thickness of the single crystal piezoelectric layer 140, and at least a part of the upper side of the single crystal piezoelectric layer 140. It includes a step of arranging the upper electrode layer 150 facing the lower electrode layer 160 via the crystalline piezoelectric layer 140, a step of forming a through groove 121, and a step of forming a recess 113. .. In the step of forming the through groove 121, the through groove 121 that penetrates at least the first laminated body 10 in the vertical direction is formed so as to divide the first protective portion 190. In the step of forming the recess 113, when viewed from the vertical direction, a portion where the upper electrode layer 150 and the lower electrode layer 160 face each other via the single crystal piezoelectric layer 140, and a through groove 121 are formed. A recess 113 that opens to the lower side of the second laminated body 20 and communicates with the through groove 121 is formed so as to overlap the located portion.

Thereby, the environmental resistance of the piezoelectric device 100 can be improved. Further, since the through groove 121 is formed by processing the first protective portion 190 which is easier to etch than the single crystal piezoelectric layer 140 made of a difficult-to-etch material, the shape of the through groove 121 is stabilized. be able to.

(Embodiment 2)
Hereinafter, the piezoelectric device according to the second embodiment of the present invention will be described. The piezoelectric device according to the second embodiment of the present invention is different from the piezoelectric device 100 according to the first embodiment of the present invention mainly in that a second protective portion is provided. Therefore, the description of the configuration similar to that of the piezoelectric device 100 according to the first embodiment of the present invention will not be repeated.

FIG. 15 is a cross-sectional view of the piezoelectric device according to the second embodiment of the present invention. The cross-sectional view of the piezoelectric device 200 shown in FIG. 15 is shown in the same cross-sectional view as the cross-sectional view of the piezoelectric device 100 shown in FIG.

As shown in FIG. 15, in the second embodiment of the present invention, the membrane portion 120 includes the first intermediate layer 270 as an intermediate layer located between the lower electrode layer 260 and the single crystal piezoelectric layer 140. .. As a result, the stress generated in the membrane portion 120 can be relaxed, and the peeling of the lower electrode layer 260 from the single crystal piezoelectric layer 140 can be suppressed.

In the piezoelectric device 200 according to the present embodiment, the membrane portion 120 includes a first intermediate layer 270 and a second intermediate layer 275 as intermediate layers, and the plurality of layers 130 constituting the membrane portion 120 are The intermediate layer includes a first intermediate layer 270 and a second intermediate layer 275.

The first intermediate layer 270 is provided so as to be in contact with each of the lower surface of the single crystal piezoelectric layer 140, the lower surface of the first protective portion 190, and the lower surface of the second protective portion described later. Is composed of a dielectric layer such as _{SiO 2.} The lower electrode layer 260 is arranged below the first intermediate layer 270. The first protective portion 190 is composed of a member integrated with the first intermediate layer 270.

The second intermediate layer 275 is provided so as to be in contact with each of the lower surface of the lower electrode layer 260 and the lower surface of the first intermediate layer 270 that are not covered by the lower electrode layer 260. The second intermediate layer 275 is preferably made of the same material as the material constituting the first intermediate layer 270. The second intermediate layer 275 is composed of a dielectric layer such as _{SiO 2.} In the present embodiment, the semiconductor layer 180 is provided so as to be in contact with the lower surface of the first intermediate layer 270.

As shown in FIG. 15, in the piezoelectric device 200 according to the second embodiment of the present invention, the single crystal piezoelectric layer 140 has a second cross section 242 above the base 110 and facing each other with a groove 143 in between. I have more. The second cross section 242 is covered with a second protective portion 291 located with the groove portion 143 in between. The lower electrode layer 260 is located below the second protective portion 291. The second external electrode 165 is provided on the lower electrode layer 260, the inner side surface of the groove portion 143, and the upper side of the second protective portion 291 and is separated from the single crystal piezoelectric layer 140.

As a result, it is possible to prevent the metal atoms constituting the second external electrode 165 from diffusing into the single crystal piezoelectric layer 140. For example, even when the second external electrode 165 is made of Ti and the single crystal piezoelectric layer 140 is made of lithium niobate, the Ti atom is a single crystal piezoelectric layer due to the above configuration. It is possible to suppress the diffusion within 140.

That is, in the present embodiment, the groove portion 143 is formed not in the single crystal piezoelectric layer 140 but in the second protective portion 291. The second cross section 242 is not exposed to the groove portion 143. In the present embodiment, the groove portion 143 is formed so as to reach the upper surface of the lower electrode layer 260. The distance between the second cross sections 242 increases from the upper electrode layer 150 side to the lower electrode layer 160 side.

The second protective portion 291 is composed of a member integrated with the first intermediate layer 270. The lower surface of the second protective portion 291 is connected to the first intermediate layer 270. The second protective portion 291 is made of a dielectric material such as _{SiO 2.}

Hereinafter, a method for manufacturing the piezoelectric device 200 according to the second embodiment of the present invention will be described.
FIG. 16 is a cross-sectional view showing a state in which a groove for a first protective portion and a groove for a second protective portion are formed in a single crystal piezoelectric layer in the method for manufacturing a piezoelectric device according to a second embodiment of the present invention. As shown in FIG. 16, the groove 141A for the first protective portion is formed, and the groove 242A for the second protective portion is formed on the lower surface of the single crystal piezoelectric layer 140 by an etching method or the like.

FIG. 17 shows the first intermediate in each of the lower surface of each single crystal piezoelectric layer, the inside of the groove for the first protection portion, and the inside of the groove for the second protection portion in the method for manufacturing the piezoelectric device according to the second embodiment of the present invention. It is sectional drawing which shows the state which provided the layer. As shown in FIGS. 16 and 17, the first protective portion groove 141A, the second protective portion groove 242A, and the lower surface of the single crystal piezoelectric layer 140 are formed by a CVD method, a PVD method, or the like. An intermediate layer 270 is provided.

FIG. 18 is a cross-sectional view showing a state in which the lower surface of the first intermediate layer is scraped in the method for manufacturing a piezoelectric device according to the second embodiment of the present invention. As shown in FIG. 18, the lower surface of the first intermediate layer 270 is scraped to be flat by CMP or the like. In this way, the first protective portion groove 141A is filled with the first protective portion 190 made of the same member as the first intermediate layer 270, and the second protective portion groove 242A is filled with the first intermediate layer 270. It is filled with the second protective portion 291 made of the same member as the above.

FIG. 19 is a cross-sectional view showing a state in which a lower electrode layer is provided on the lower surface of the first intermediate layer in the method for manufacturing a piezoelectric device according to the second embodiment of the present invention. As shown in FIG. 19, the lower electrode layer 260 is provided on the lower surface of the first intermediate layer 270. In the present embodiment, the specific method for providing the lower electrode layer 260 is the same as the method for providing the lower electrode layer 160 in the first embodiment of the present invention.

FIG. 20 is a cross-sectional view showing a state in which a second intermediate layer is provided on the lower surfaces of each of the first intermediate layer and the lower electrode layer in the method for manufacturing a piezoelectric device according to the second embodiment of the present invention. As shown in FIG. 20, a second intermediate layer 275 is provided on the lower surfaces of each of the first intermediate layer 270 and the lower electrode layer 260 by a CVD method, a PVD method, or the like.

FIG. 21 is a cross-sectional view showing a state in which the lower surface of the second intermediate layer is scraped in the method for manufacturing a piezoelectric device according to the second embodiment of the present invention. As shown in FIG. 21, the lower surface of the second intermediate layer 275 is flattened by CMP or the like.

In the present embodiment, the first laminated body 10 is formed by the above steps. Specifically, the first laminated body 10 in the present embodiment includes a first intermediate layer 270 and a second intermediate layer 275 as intermediate layers, and further includes a second protective portion 291.

FIG. 22 is a cross-sectional view showing a state in which the second laminated body is bonded to the lower surface of the second intermediate layer in the method for manufacturing a piezoelectric device according to the second embodiment of the present invention. FIG. 23 is a cross-sectional view showing a state in which the second laminated body is bonded to the lower surface of the second intermediate layer in the method for manufacturing a piezoelectric device according to the second embodiment of the present invention. As shown in FIGS. 22 and 23, the second laminated body 20 used in the first embodiment of the present invention is joined to the lower side of the first laminated body 10.

FIG. 24 is a cross-sectional view showing a state in which the upper surfaces of the single crystal piezoelectric layer, the first protective portion, and the second protective portion are scraped in the method for manufacturing the piezoelectric device according to the second embodiment of the present invention. As shown in FIG. 24, the upper surfaces of the single crystal piezoelectric layer 140, the first protective portion 190, and the second protective portion 291 are each scraped by CMP or the like to make the single crystal piezoelectric layer 140 a desired thickness. , Each of the first protection unit 190 and the second protection unit 291 is exposed.

FIG. 25 is a cross-sectional view showing a state in which an upper electrode layer is provided on the upper surface of the single crystal piezoelectric layer in the method for manufacturing a piezoelectric device according to the second embodiment of the present invention. As shown in FIG. 25, the upper electrode layer 150 is arranged on the upper surface of the single crystal piezoelectric layer 140 in the same manner as the upper electrode layer 150 in the first embodiment of the present invention.

FIG. 26 is a cross-sectional view showing a state in which a through groove is formed from the first protective portion to the semiconductor layer in the method for manufacturing a piezoelectric device according to the second embodiment of the present invention. As shown in FIG. 26, the through groove 121 is formed in the same manner as the through groove 121 in the first embodiment of the present invention. In the present embodiment, the through groove 121 is formed so as to penetrate the first intermediate layer 270 and the second intermediate layer 275.

FIG. 27 is a cross-sectional view showing a state in which a groove portion is formed from the second protective portion to the first intermediate layer in the method for manufacturing a piezoelectric device according to the second embodiment of the present invention. As shown in FIG. 27, the groove portion 143 is formed by etching the second protective portion 291 and the first intermediate layer 270 above the base portion 110.

FIG. 28 is a cross-sectional view showing a state in which the first external electrode is provided on the upper electrode layer and the second external electrode is provided on the lower electrode layer in the method for manufacturing a piezoelectric device according to the second embodiment of the present invention. .. As shown in FIG. 28, the first external electrode 155 and the second external electrode 165 are provided in the same manner as the first external electrode 155 and the second external electrode 165 in the first embodiment of the present invention.

Finally, as shown in FIGS. 28 and 15, the recess 113 is formed in the same manner as the recess 113 of the first embodiment of the present invention. By the above steps, the piezoelectric device 200 according to the second embodiment of the present invention as shown in FIG. 15 is manufactured.

(Embodiment 3)
Hereinafter, the piezoelectric device according to the third embodiment of the present invention will be described. The piezoelectric device according to the third embodiment of the present invention is different from the piezoelectric device 200 according to the second embodiment of the present invention mainly in that it does not have the first intermediate layer 270 in the second embodiment of the present invention. Therefore, the description of the configuration similar to that of the piezoelectric device 200 according to the second embodiment of the present invention will not be repeated.

FIG. 29 is a cross-sectional view of the piezoelectric device according to the third embodiment of the present invention. The cross-sectional view of the piezoelectric device 300 shown in FIG. 29 is shown in the same cross-sectional view as the cross-sectional view of the piezoelectric device 200 shown in FIG.

As shown in FIG. 29, in the third embodiment of the present invention, the membrane portion 120 includes only the second intermediate layer 275 as the intermediate layer. The lower electrode layer 260 is provided on the lower surface of the single crystal piezoelectric layer 140, the lower surface of the second external electrode 165, and the lower surface of the second protective portion 291. As a result, in the membrane portion 120, the upper electrode layer 150 and the lower electrode layer 260 face each other with only the single crystal piezoelectric layer 140 interposed therebetween, so that the piezoelectric device 200 is compared with the piezoelectric device 200 according to the second embodiment of the present invention. The piezoelectric characteristics of the device 300 can be improved.

In the present embodiment, as the intermediate layer, the second intermediate layer 275 is provided on the lower surface of the single crystal piezoelectric layer 140, the lower surface of the lower electrode layer 260, and the lower surface of the first protective portion 190.

Hereinafter, a method for manufacturing the piezoelectric device according to the third embodiment of the present invention will be described.
First, as shown in FIGS. 16 and 17, in the same manner as in the manufacturing method of the piezoelectric device 200 according to the second embodiment of the present invention, the inside of the first protective portion groove 141A, the inside of the second protective portion groove 242A, and the single. A first intermediate layer 270 is provided on the lower surface of each of the crystalline piezoelectric layers 140.

Next, scrape the first intermediate layer 270 from the bottom. FIG. 30 is a cross-sectional view showing a state in which the first intermediate layer is scraped from the lower side in the method for manufacturing a piezoelectric device according to the third embodiment of the present invention. As shown in FIG. 30, the first intermediate layer 270 is scraped from the lower side by CMP or the like to completely remove the first intermediate layer 270 located below the lower surface of the single crystal piezoelectric layer 140. At this time, the lower surface of the single crystal piezoelectric layer 140 may be scraped at the same time.

FIG. 31 is a cross-sectional view showing a state in which the lower electrode layer is provided on the lower surface of the single crystal piezoelectric layer and the second protective portion in the method for manufacturing the piezoelectric device according to the third embodiment of the present invention. As shown in FIG. 31, the lower electrode layer 260 is provided on the lower surface of the single crystal piezoelectric layer 140 and the lower surface of the second protective portion 291. In the present embodiment, the specific method for providing the lower electrode layer 260 is the same as the method for providing the lower electrode layer 160 in the first embodiment of the present invention.

FIG. 32 is a cross-sectional view showing a state in which a second intermediate layer is provided on the lower surfaces of each of the first protective portion and the single crystal piezoelectric layer in the method for manufacturing a piezoelectric device according to the third embodiment of the present invention. As shown in FIG. 32, a second intermediate layer 275 is provided on the lower surfaces of each of the single crystal piezoelectric layer 140, the lower electrode layer 260, and the first protective portion 190 by a CVD method, a PVD method, or the like.

In the present embodiment, after the second intermediate layer 275 is provided, the book as shown in FIG. 29 is similar to the method for manufacturing the piezoelectric device 200 according to the second embodiment of the present invention shown in FIGS. 21 to 28. The piezoelectric device 300 according to the third embodiment of the present invention can be manufactured.

(Embodiment 4)
Hereinafter, the piezoelectric device according to the fourth embodiment of the present invention will be described. The piezoelectric device according to the fourth embodiment of the present invention is different from the piezoelectric device 200 according to the second embodiment of the present invention mainly in that the lower electrode layer is a semiconductor layer. Therefore, the description of the configuration similar to that of the piezoelectric device 200 according to the second embodiment of the present invention will not be repeated.

FIG. 33 is a cross-sectional view of the piezoelectric device according to the fourth embodiment of the present invention. The cross-sectional view of the piezoelectric device 400 shown in FIG. 33 is shown in the same cross-sectional view as the cross-sectional view of the piezoelectric device 200 shown in FIG.

As shown in FIG. 33, in the present embodiment, the lower electrode layer 460 is a semiconductor layer 180. That is, as shown in FIG. 15, the lower electrode layer 260 and the second intermediate layer 275 made of members different from the semiconductor layer 180 in the second embodiment of the present invention are the piezoelectric device 400 according to the fourth embodiment of the present invention. Not provided in. As shown in FIG. 33, in the present embodiment, the semiconductor layer 180 is provided on the lower surface of the first intermediate layer 270.

Since the lower electrode layer 460 is the semiconductor layer 180, the step of providing the lower electrode layer made of a member different from the semiconductor layer 180 can be omitted when manufacturing the piezoelectric device 400. As a result, the manufacturing method of the piezoelectric device 400 can be simplified.

In the present embodiment, the electrical resistivity of the material constituting the semiconductor layer 180 is preferably 20 mΩ · cm or less from the viewpoint of functioning as the lower electrode layer 460.

In the present embodiment, the groove portion 443 is located below the upper surface of the semiconductor layer 180. As a result, the contact area between the second external electrode 165 and the semiconductor layer 180, which is the lower electrode layer 460, increases. Therefore, the contact resistance between the second external electrode 165 and the semiconductor layer 180 can be reduced.

Hereinafter, a method for manufacturing the piezoelectric device according to the fourth embodiment of the present invention will be described.
First, in the same manner as the manufacturing method of the piezoelectric device 200 according to the second embodiment of the present invention shown in FIGS. 16 to 18, the groove 141A for the first protective portion is filled with the first protective portion 190, and the second protective portion is formed. The groove 242A is filled with the second protective portion 291. In the method for manufacturing the piezoelectric device 400 according to the fourth embodiment of the present invention, the laminate shown in FIG. 18 is the first laminate 10.

FIG. 34 is a cross-sectional view showing a state in which the second laminated body is bonded to the lower surface of the first intermediate layer in the method for manufacturing a piezoelectric device according to the fourth embodiment of the present invention. FIG. 35 is a cross-sectional view showing a state in which the second laminated body is bonded to the lower surface of the first intermediate layer in the method for manufacturing the piezoelectric device according to the fourth embodiment of the present invention.

As shown in FIGS. 34 and 35, the second laminated body 20 used in the first embodiment of the present invention is joined to the lower side of the first laminated body 10.

FIG. 36 is a cross-sectional view showing a state in which the upper surfaces of the single crystal piezoelectric layer, the first protective portion, and the second protective portion are scraped in the method for manufacturing the piezoelectric device according to the fourth embodiment of the present invention. As shown in FIG. 36, the upper surfaces of the single crystal piezoelectric layer 140, the first protective portion 190, and the second protective portion 291 are each scraped by CMP or the like to make the single crystal piezoelectric layer 140 a desired thickness. Each of the first protective portion 190 and the second protective portion 291 is exposed.

FIG. 37 is a cross-sectional view showing a state in which an upper electrode layer is provided on the upper surface of the single crystal piezoelectric layer in the method for manufacturing a piezoelectric device according to the fourth embodiment of the present invention. As shown in FIG. 37, the upper electrode layer 150 is arranged on the upper surface of the single crystal piezoelectric layer 140 in the same manner as the upper electrode layer 150 in the first embodiment of the present invention.

FIG. 38 is a cross-sectional view showing a state in which a through groove is formed from the first protective portion to the semiconductor layer in the method for manufacturing a piezoelectric device according to the fourth embodiment of the present invention. As shown in FIG. 38, the through groove 121 is formed in the same manner as the through groove 121 in the first embodiment of the present invention.

FIG. 39 is a cross-sectional view showing a state in which a groove portion is formed from the second protective portion to the semiconductor layer in the method for manufacturing a piezoelectric device according to the fourth embodiment of the present invention. As shown in FIG. 39, the groove portion 443 is formed by etching the second protective portion 291 and the first intermediate layer 270 and a part of the semiconductor layer 180 above the base portion 110.

FIG. 40 shows a state in which the first external electrode is provided on the upper electrode layer and the second external electrode is provided on the semiconductor layer which is the lower electrode layer in the method for manufacturing the piezoelectric device according to the fourth embodiment of the present invention. It is a sectional view. As shown in FIG. 40, the first external electrode 155 and the second external electrode 165 are provided in the same manner as the first external electrode 155 and the second external electrode 165 in the first embodiment of the present invention. That is, in the fourth embodiment of the present invention, the second external electrode 165 is provided on the semiconductor layer 180, which is the lower electrode layer 460.

Finally, as shown in FIGS. 40 and 33, the recess 113 is formed in the same manner as the recess 113 of the first embodiment of the present invention. By the above steps, the piezoelectric device 400 according to the fourth embodiment of the present invention as shown in FIG. 33 is manufactured.

In the above description of the embodiment, the configurations that can be combined may be combined with each other.

The embodiments disclosed this time should be considered to be exemplary in all respects and not restrictive. The scope of the present invention is shown by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the claims.

10 1st laminate, 20 2nd laminate, 100, 200, 300, 400 piezoelectric device, 110 base, 110a lower base, 110b upper base, 111 upper main surface, 112 lower main surface, 113 recess, 120 membrane Part, 121 through groove, 130 multiple layers, 140 single crystal piezoelectric layer, 141 first cross section, 141A first protection groove, 142, 242 second cross section, 143, 443 groove, 150 upper electrode layer, 155th 1 external electrode, 160, 260, 460 lower electrode layer, 161 etching stop layer, 165 second external electrode, 170 intermediate layer, 180 semiconductor layer, 190 first protective part, 242A second protective part groove, 270 first intermediate Layer, 275, second intermediate layer, 291 second protection.

Claims (7)

1. At the base,
   It is indirectly supported by the base portion, is located above the base portion, and includes a membrane portion composed of a plurality of layers.
   The membrane portion does not overlap the base portion, and the single crystal piezoelectric layer, an upper electrode layer arranged on the upper side of the single crystal piezoelectric layer, and the single crystal piezoelectric layer are interposed therein. Includes a lower electrode layer arranged to face at least a portion of the upper electrode layer.
   The membrane portion is provided with a through groove that penetrates in the vertical direction.
   A piezoelectric device in which a first cross section of the single crystal piezoelectric layer facing the through groove is covered with a first protective portion located with the through groove in between.
2. The piezoelectric device according to claim 1, wherein the distance between the first cross sections increases from the upper electrode layer side to the lower electrode layer side.
3. The piezoelectric device according to claim 1 or 2, wherein the membrane portion further includes an intermediate layer located between the lower electrode layer and the single crystal piezoelectric layer.
4. Further, a second external electrode electrically connected to the lower electrode layer is provided.
   The plurality of layers extend above the base and extend over the base.
   The single crystal piezoelectric layer further has a second cross section above the base portion, which faces each other with a groove portion in between.
   The second cross section is covered with a second protective portion located with the groove portion in between.
   The lower electrode layer is located below the second protective portion.
   The second external electrode is provided on the lower electrode layer, the inner surface of the groove portion, and the upper side of the second protective portion, and is separated from the single crystal piezoelectric layer. The piezoelectric device according to any one of claims 1 to 3.
5. The piezoelectric device according to any one of claims 1 to 4, wherein the lower electrode layer is a semiconductor layer.
6. The lower electrode layer is a semiconductor layer,
   The piezoelectric device according to claim 4, wherein the groove is located below the upper surface of the semiconductor layer.
7. The process of arranging the lower electrode layer below the single crystal piezoelectric layer,
   A step of forming a groove for a first protective portion penetrating in the vertical direction in the single crystal piezoelectric layer, and
   The step of filling the groove for the first protective portion with the first protective portion and
   The step of forming the first laminated body including at least the single crystal piezoelectric layer, and
   A step of joining the second laminated body to the lower side of the first laminated body,
   The step of adjusting the thickness of the single crystal piezoelectric layer and
   A step of arranging an upper electrode layer on the upper side of the single crystal piezoelectric layer, at least a part of which faces the lower electrode layer via the single crystal piezoelectric layer.
   A step of forming a through groove that penetrates at least the first laminated body in the vertical direction so as to divide the first protective portion.
   When viewed from the vertical direction, the upper electrode layer and the lower electrode layer overlap with each other through the single crystal piezoelectric layer and the portion where the through groove is located. A method for manufacturing a piezoelectric device, comprising a step of forming a recess that opens on the lower side of the second laminated body and communicates with the through groove.

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