Patent Description:
Conventionally, a piezoelectric device, which makes use of the piezoelectric effect of a substance, has been adopted. The piezoelectric effect is a phenomenon in which microscopic polarization occurs in proportion to a pressure applied to a substance. Various sensors such as pressure sensors, acceleration sensors, or acoustic emission (AE) sensors for detecting elastic waves have been manufactured by utilizing the piezoelectric effect.

In recent years, touch panels have been used as input interfaces of information processing devices such as smartphones, and applying piezoelectric devices to touch panels is increasing. A touch panel is integrated into the display device of an information processing device, and high transparency to visible light is required to improve the visibility. On the other hand, it is desirable for the piezoelectric layer to be highly responsive to pressure in order to accurately detect operations by a finger.

A configuration of a cantilever type deformable device having a stack of a piezoelectric film and electrodes for deforming the piezoelectric film by the inverse piezoelectric effect, in which the edges of the electrodes of the respective layers are arranged so as not to align on the same straight line extending in the film thickness direction, is known. (See, for example, Patent Document <NUM>). In this structure, the stress concentration due to deformation during driving the device is reduced by making the lowermost electrode the largest and by reducing the electrode size toward the upper layer.

<CIT> discloses a surface acoustic wave element having an interdigital transducer (IDT) electrode formed on one side of the piezoelectric member.

<CIT> illustrates a solid-state-sheer-stress sensor where a top electrode and a bottom electrode are disposed adjacent to both surfaces of a piezoelectric sensing material.

<CIT> reveals an inkjet printhead comprising a thin film stack with a substrate, an adhesive layer, a bottom metal electrode, a piezoelectric layer and a second top metal electrode.

Microcracking often occurs in piezoelectric layers due to surface roughness of, or foreign substances on the substrates. Such microcracks may form a leakage path that electrically cause a short-circuit between the top and bottom electrodes. This phenomenon becomes more prominent as the piezoelectric film is thinner.

An objective of the invention is to provide a structure capable of suppressing leakage current between electrodes which sandwich a piezoelectric layer, and reducing deterioration in piezoelectric characteristics.

The present invention is directed to a piezoelectric device according to the independent device claim <NUM> and to a method of manufacturing a piezoelectric device according to the independent claim <NUM>.

In one example, the first electrode is formed in a pattern having two or more stripes, and the second electrode is formed in an area corresponding to spaces between adjacent stripes of the first electrode.

In another example, one of the first electrode and the second electrode is formed in a patch pattern, and the other of the first electrode and the second electrode is formed in a planar pattern obtained by cutting away the patch pattern.

With the above-described configurations, leakage current between electrodes sandwiching the piezoelectric layer can be suppress, and deterioration in the piezoelectric characteristics can be reduced.

<FIG> is a diagram more particularly illustrating a technical issue of microcracking found by the inventors. In general, a layered structure in which a piezoelectric layer <NUM> is provided between electrodes <NUM> and <NUM> is provided on a substrate <NUM> from the viewpoint of convenience of the manufacturing process and structural stability.

In the ideal state shown in <FIG>, electrical charges with a specific polarity (for example, positive charges) appear at or near the interface between the piezoelectric layer <NUM> and the electrode <NUM>, and electrical charges with an opposite polarity (for example, negative charges) appear at or near the interface between the piezoelectric layer <NUM> and the electrode <NUM>, upon application of pressure. In contrast, when the piezoelectric layer <NUM> is pulled in the thickness direction, negative charges appear at the interface between the piezoelectric layer <NUM> and the electrode <NUM>, and positive charges appear at the interface between the piezoelectric layer <NUM> and the electrode <NUM>. Thus, mechanical energy can be converted into electrical energy by making use of polarization of the crystal structure of the piezoelectric layer <NUM>.

As shown in <FIG>, if foreign substances, protrusions, pinholes, or the like are present on the surface of the substrate <NUM> or the surface of the electrode <NUM>, microcracks starting from these surface irregularities may be induced in the piezoelectric layer <NUM>. If such microcracks run through the piezoelectric layer <NUM> in the thickness direction, a leakage path may be formed between the electrodes <NUM> and <NUM>. In this case, the produced polarized charges are cancelled, and the piezoelectric effect disappears.

If the substrate <NUM> is made of a plastic, a resin, or the like, the surface tends to be rough or uneven. The surface roughness of the substrate <NUM> cannot be absorbed by the metal crystals of the overlying electrode <NUM>. The surface of the metal film of the electrode <NUM> also becomes uneven, reflecting the surface state of the substrate <NUM>. Cracking is likely to occur directly above foreign matters, protrusions, pinholes, or the like that may be present at the interface between the electrode <NUM> and the piezoelectric layer <NUM>.

In the embodiment, to suppress the occurrence of a leakage path running between the electrodes provided on both sides of the piezoelectric layer, a piezoelectric device is configured such that the electrodes do not overlap each other in the stacking direction. Even without overlapping of the electrodes in the stacking direction, electrical charges are uniformly distributed at the surface or the interface of the piezoelectric film, and can be appropriately extracted. By configuring the electrodes so as not to overlap in the stacking direction, an additional advantageous effect that the stress is reduced and bending of the layered structure is suppressed, can also be achieved. In this specification and appended claims, the expression that the electrodes "do not overlap" in the stacking direction means that almost all the parts of the bottom electrode and the top electrode do not overlap each other, viewed in the stacking direction. A slight overlap, which may be caused by variations in the edge position or the size of the electrodes due to manufacturing errors, design around, or the like is also within the scope of the configuration of the electrodes which "do not overlap" each other.

<FIG> is a schematic diagram of a piezoelectric device 10A according to the first embodiment. <FIG> shows a top view, and (B) shows a cross-sectional view taken along the I-I' line of (A). The piezoelectric device 10A has a first electrode <NUM> formed on a substrate <NUM>, a piezoelectric layer <NUM> provided on the first electrode <NUM>, and a second electrode <NUM> provided on the piezoelectric layer <NUM>. The directional term "on" does not intend the absolute direction, and it merely denotes the upper side when viewed in the stacking direction.

The first electrode <NUM> and the second electrode <NUM> are formed in stripe patterns extending in the same direction, but are arranged so as not to overlap each other viewed in the cross-section taken in the thickness direction. The second electrode <NUM> is provided in a region corresponding to the space between adjacent stripes of the first electrode <NUM>.

With this configuration, when pressure is applied to the piezoelectric layer <NUM>, surface charges appear in the piezoelectric layer <NUM>, and a voltage is generated. By measuring the electric current, the polarization proportional to the pressure can be known. The unit cell of the crystal structure of the piezoelectric layer <NUM> does not have a point-symmetric center, and the atom at the crystal center is offset from the point-symmetric center of the crystal, for example, upward in the crystal growth direction. In this case, the positive charges are biased to the interface between the piezoelectric layer <NUM> and the upper electrode <NUM>, and the negative charges are biased to the interface between the piezoelectric layer <NUM> and the lower electrode <NUM>. Without application of a pressure, these charges are neutralized by being combined with floating charges in the air or other charges on the metal surface, and no voltage is generated.

When a pressure is applied to the piezoelectric layer <NUM> from, for example, the upper electrode <NUM>, the atom at the crystal center moves closer to the point-symmetric center, and the polarization in the piezoelectric layer <NUM> decreases. In other words, the amount of charges having been distributed near the interface decreases. As a result, those charges that have been paired up with the vanished charges become surplus, and a voltage is generated. These excess charges are also uniformly distributed near the interface, and accordingly, the change in the polarization state due to application of the pressure can be detected, even if the upper electrode <NUM> and the lower electrode <NUM> do not overlap each other in the film thickness direction or the stacking direction.

With this structure, even if microcracking occurs, starting from a foreign matter, a protrusion, or a pinhole that may be preset on the surface of the substrate <NUM> or the electrode <NUM>, and even if such microcracking extends in the thickness direction, the formation of a leakage path that electrically short-cuts the lower electrode <NUM> and the upper electrode <NUM> can be suppressed.

The piezoelectric device 10A may be fabricated by the following process. First, the electrode <NUM> is formed on the substrate <NUM>. The material of the substrate <NUM> is arbitrary, and it may be a substrate made of an inorganic material such as a glass substrate, a sapphire substrate, or an MgO substrate, or alternatively, it may be a plastic substrate. With an inorganic substrate, the surface is smooth with few protrusions or pinholes that may cause cracking, and the occurrence of cracking itself can be reduced. With a plastic or resin substrate, the surface tends to be uneven, but it is flexible, easy to handle, and has a wide range of application.

Because the piezoelectric device 10A is designed such that the electrodes <NUM> and <NUM> do not overlap each other in the film thickness direction or the stacking direction, formation of a leakage path can be suppressed even if the surface of the substrate <NUM> is not even. The substrate <NUM> may be made of a polymer such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), acrylic resin, cycloolefin polymer, polyimide (PI), or the like. Of these, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), acrylic resin, and cycloolefin polymer are colorless and transparent materials, and are suitable for applications in which light is transmitted through the back surface of the substrate <NUM>.

The electrode <NUM> is formed on the substrate <NUM>. The electrode can be formed of an appropriate conductor, and it may be formed of, for example, a transparent amorphous oxide conductor. Such an oxide conductor may be "transparent" to visible light, or "transparent" to light in a specific wavelength band to be used, depending on the application of the piezoelectric device 10A.

For the transparent amorphous oxide conductor, indium tin oxide (ITO), indium zinc oxide (IZO), etc. can be used. An electrode film with a thickness of <NUM>-<NUM>, preferably <NUM>-<NUM> may be formed using these materials by direct current (DC) or radio frequency (RF) magnetron sputtering. The electrode film can be patterned into the electrode <NUM> by an ordinary technique of photolithography and wet etching.

If ITO is used, the tin (Sn) content ratio Sn/(In + Sn) may be, for example, <NUM> to <NUM> wt%. Within this range, amorphous ITO transparent to visible light can be formed by means of sputtering at room temperature.

If IZO is used, the zinc (Zn) content ratio Zn/(In + Zn) may be, for example, around <NUM> wt%. IZO is also transparent to visible light, and an amorphous film can be formed by sputtering at room temperature.

Next, the piezoelectric layer <NUM> is formed over electrode <NUM> and the substrate <NUM> by sputtering. The piezoelectric layer <NUM> is formed of a piezoelectric material having a wurtzite crystal structure, and its thickness is <NUM> to <NUM>, for example.

If the thickness of the piezoelectric layer <NUM> is less than <NUM>, the first electrode <NUM> and the second electrode <NUM> are too close to each other. In this case, the influence of the microcracking becomes relatively conspicuous, and it may be difficult to suppress leakage current even if the lower electrode and the upper electrode do not overlap each other in the thickness direction. Accordingly, the thickness of the piezoelectric layer <NUM> is preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>.

By employing a sputtering process to form the electrode <NUM> and the piezoelectric layer <NUM>, uniform films can be formed with sufficient adhesion, while maintaining the composition ratios of the compounds of the targets. In addition, a film can be accurately formed to a desired thickness simply by controlling the time.

A wurtzite crystal structure is represented by general formula AB, where A is a positive cation (An+) and B is a negative anion (Bn-). It is desirable to select a wurtzite piezoelectric material which can express piezoelectric properties to a certain degree or higher, and which can be crystallized in a low temperature process at or below <NUM>. For example, zinc oxide (ZnO), zinc sulfide (ZnS), zinc selenide (ZnSe), zinc telluride (ZnTe), aluminum nitride (AlN), gallium nitride (GaN), cadmium selenide (CdSe), cadmium telluride (CdTe), silicon carbide (SiC), etc. can be used. Any one or a combination of two or more of these components may be used.

When two or more of components are combined, the respective layers of the selected components may be formed one by one, or alternatively, a single layer may be formed simultaneously using the targets of the selected components. The selected one or the combination of two or more of the components may be used as the main component, and other components may be optionally added. The content of the optionally added sub-component is not particularly limited as long as the advantageous effect of the present invention can be achieved. The content of such a sub-component other than the main component is, for example, from <NUM> to <NUM> at.

For example, a wurtzite material containing ZnO or AlN as the main component is used. A metal which does not cause the main component to exhibit conductivity when incorporated into the main component may be added as a dopant. Such dopants may include silicon (Si), magnesium (Mg), vanadium (V), titanium (Ti), zirconium (Zr), lithium (Li), etc. One or a combination of two or more of the above-described dopants may be added. By adding one or more of these metals as a dopant, the occurrence of cracking can be reduced. When a transparent wurtzite crystalline material is used for the piezoelectric layer, the layered structure is suitable for use in a display.

Next, the electrode <NUM> is formed into a predetermined pattern on the piezoelectric layer <NUM>. The electrode <NUM> is formed so as not to overlap the pattern of the electrode <NUM> in the film thickness or the stacking direction. If the lower electrode <NUM> is formed in a stripe or a line-and-space pattern, then the electrode <NUM> is formed so as to fill the area corresponding to the space between adjacent stripes of the electrode <NUM>.

The electrode <NUM> may be formed of a transparent amorphous oxide conductor, or a good conductor such as a metal or an alloy. When a transparent amorphous oxide conductor is used, an ITO film having a thickness of <NUM> to <NUM> may be formed at room temperature by DC or RF magnetron sputtering, and patterned into a predetermined shape by photolithography and etching. The material of the electrode <NUM> may be the same as, or different from that of the electrode <NUM>.

By forming the electrode <NUM> with an amorphous oxide conductor, undesirable protrusions or pinholes, which may cause microcracking, can be reduced on the surface of the electrode <NUM>.

<FIG> is a schematic diagram of a piezoelectric device 10B according to the second embodiment. <FIG> shows a top view, and (B) shows a cross-sectional view taken along the e II-II' line. Similar to the first embodiment, the second embodiment also provides a configuration in which a pair of electrodes provided on both sides a piezoelectric layer do not overlap each other in the film thickness direction or the stacking direction.

The piezoelectric device 10B has a first electrode <NUM> formed on a substrate <NUM>, a piezoelectric layer <NUM> provided on the first electrode <NUM>, and a second electrode <NUM> provided on the piezoelectric layer <NUM>. Again, the directional term "on" indicates the upper side when viewed in the stacking direction.

The first electrode <NUM> and the second electrode <NUM> have complementary planar shapes. In the example of <FIG>, the second electrode <NUM> is a round electrode, and the first electrode <NUM> has a pattern complementary with the round shape, namely a pattern that the circle is cut off from the solid film. Off course, the shape of the electrode <NUM> is not limited to the circle, and it may be an ellipse, a polygon, or other patch shapes. As to the polygon, any polygonal shape such as a triangle, a rectangle, a hexagon, an octagon, etc. can be adopted.

The other electrode <NUM>, which is paired with the electrode <NUM>, has a pattern complementary with the shape of the electrode <NUM>, where the shape of the electrode <NUM> is cut out from the solid film. It is unnecessary that the upper electrode <NUM> provided on the piezoelectric layer <NUM> is always patterned in the patch shape such as a circle, a polygon, or the like, and instead, the lower electrode <NUM> may be formed in a patch pattern. In such a case, the upper electrode <NUM> is formed in a pattern complementary with the patch shape of the lower electrode <NUM>. The stripe pattern of the first embodiment may also be called a complementary electrode pattern in terms that the upper and lower electrodes do not overlap each other.

In this configuration, when pressure is applied to the piezoelectric layer <NUM>, positive charges appear on one of the surfaces of the piezoelectric layer <NUM> (for example, at the interface with the upper electrode <NUM>), and negative charges appear and on the other surface (for example, at the interface with the lower electrode <NUM>). By measuring the current flowing through the electrodes <NUM> and <NUM>, the pressure applied to the piezoelectric layer <NUM> can be detected.

Owing to this structure, a leakage path can be prevented from being formed and short-circuiting between the lower electrode <NUM> and the upper electrode <NUM> even if microcracking is induced and extends in the thickness direction starting from a foreign matter, a protrusions, a pinholes, or the like that may be present on the surface of the substrate <NUM> or the electrode <NUM>.

The manufacturing process of the piezoelectric device 10B is basically the same as that of the piezoelectric device 10A, and only the shapes of the electrodes <NUM> and <NUM> to be formed are different. Any suitable material can be used for the substrate <NUM>, and a substrate made of an inorganic material such as a glass, sapphire, or MgO, or alternatively, a plastic substrate may be used. By using a plastic or resin substrate <NUM>, the scope of applications is expanded in terms of flexibility and easiness to handle.

The electrode <NUM> may be formed of an appropriate conductor on the substrate <NUM>. Depending on the application of the piezoelectric device 10B, the electrode <NUM> may be formed of a transparent conductive film "transparent" with respect to visible light or a target wavelength.

The piezoelectric layer <NUM> may be formed of a piezoelectric material having a wurtzite crystal structure, as in the first embodiment. Such a piezoelectric material is, for example, zinc oxide (ZnO), zinc sulfide (ZnS), zinc selenide (ZnSe), zinc telluride (ZnTe), aluminum nitride (AlN), gallium nitride (GaN), cadmium selenide (CdSe), Cadmium telluride (CdTe), silicon carbide (SiC), etc. Any one or a combination of two or more of these components may be used.

When two or more components are combined, the respective layers of the selected components may be formed one by one, or alternatively, a single layer may be formed simultaneously using the targets of the selected components. The selected one or the combination of two or more of the compounds may be used as the main component, and other components may be optionally added. The content of the optionally added sub-component is not particularly limited as long as the advantageous effect of the present invention is achieved. The content of such a sub-component is, for example, from <NUM> to <NUM> at. %, preferably, from <NUM> to <NUM> at. %, more preferably from <NUM> to <NUM> at.

The upper electrode <NUM> may have any pattern that does not overlap the pattern of the electrode <NUM> in the film thickness or the stacking direction, and it may be formed of a transparent amorphous oxide conductor, or a good conductor such as a metal or an alloy. If a transparent amorphous oxide conductor is used, an ITO film having a thickness of <NUM> to <NUM> may be formed at room temperature by, for example, DC or RF magnetron sputtering, and patterned into a predetermined shape by photolithography and etching. The material of the electrode <NUM> may be the same as, or different from the material of the electrode <NUM>.

The configuration of the second embodiment enables electric charges produced in the piezoelectric layer to be extracted, while suppressing a leakage path from being formed between the upper and lower electrodes. In addition, because of the complementary electrode patterns formed on the upper side and the bottom side of the piezoelectric layer <NUM>, a stress relaxation effect can also be expected.

<FIG> is a schematic diagram of a piezoelectric device 10C according to the third embodiment. <FIG> shows a top view, and (B) shows a cross-sectional view taken along the III-III' line. The piezoelectric device 10C has stripe electrode patterns similar to those of the first embodiment, as the complementary electrode patterns that do not overlap each other in the stacking direction.

In the third embodiment, an amorphous layer <NUM> is provided between the piezoelectric layer <NUM> and the substrate <NUM>. The lower electrode <NUM> is formed on the amorphous layer <NUM>. By providing the amorphous layer <NUM> on the substrate <NUM>, roughness or unevenness of the underlayer can be absorbed even if a plastic substrate is used, and irregularities such as protrusions, pinholes or the like, which may be induced at the surface of the electrode <NUM>, can be reduced. The surface of the amorphous layer <NUM> itself is smooth, and is thus unlikely to induce cracking in the piezoelectric layer.

If a plastic or a resin such as PET, PEN, PC, or an acrylic resin is used as the substrate <NUM>, the amorphous layer <NUM> may be an organic amorphous layer. Examples of the amorphous organic material include, but are not limited to, acrylic resin, urethane resin, melamine resin, alkyd resin, and siloxane-based polymer. In particular, it is preferable to use a thermosetting resin composed of a mixture of a melamine resin, an alkyd resin and an organic silane condensation, as the organic substance. The organic amorphous layer is formed by a coating method, a spray method, or the like.

If the amorphous organic material used for the amorphous layer <NUM> is electrically conductive, the amorphous layer <NUM> may serve as a part of the electrode <NUM>. Because the amorphous layer <NUM> absorbs the roughness or unevenness present at the surface of the substrate <NUM>, and because the amorphous layer <NUM> itself has a smooth surface, cracking is unlikely to be induced from an area of the amorphous layer <NUM> facing the electrode <NUM>.

Owing to this structure, the formation of a leakage path between the electrodes <NUM> and <NUM>, provided on both sides of the piezoelectric layer <NUM> in the stacking direction, can be suppressed.

Other configurations, materials, and fabrication steps of the piezoelectric device 10C are the same as those in the first embodiment, and redundant description will be omitted.

The configuration of the third embodiment enables electric charges produced in the piezoelectric layer to be extracted, while effectively suppressing a leakage path from being formed between the upper and lower electrodes. In addition, because of the complementary electrode patterns formed on the upper side and the bottom side of the piezoelectric layer <NUM>, a stress relaxation effect can also be expected.

<FIG> is a schematic diagram of a piezoelectric device 10D according to the fourth embodiment. <FIG> shows a top view, and (B) shows a cross-sectional view taken along the IV-IV' line. The piezoelectric device 10D employs a patch pattern and an inverted patch pattern, which corresponds to the remaining area after the patch is cut out, as the electrode patterns that do not overlap each other in the stacking direction, as in the second embodiment. The patch pattern is not limited to the round shape, and it may be an ellipse, a polygon, a rectangle, or the like.

In the fourth embodiment, an amorphous layer <NUM> is inserted between the piezoelectric layer <NUM> and the substrate <NUM>, as in the third embodiment. The lower electrode <NUM> is formed on the amorphous layer <NUM>. By providing the amorphous layer <NUM> on the substrate <NUM>, roughness or unevenness of the underlayer can be absorbed when the substrate <NUM> is plastic, and protrusions, pinholes, or the like which may occur on the surface of the electrode <NUM> can be reduced. The surface of the amorphous layer <NUM> itself is smooth, and cracking is unlikely to be induced.

Other configurations, materials, and fabrication steps of the piezoelectric device 10D are the same as those in the second embodiment, and redundant description will be omitted.

The configuration of the fourth embodiment enables electric charges produced in the piezoelectric layer to be extracted, while effectively suppressing a leakage path from being formed between the upper and lower electrodes. In addition, because of the complementary electrode patterns formed on the upper side and the bottom side of the piezoelectric layer <NUM>, a stress relaxation effect can also be expected.

<FIG> shows other modified embodiments of the electrode pattern. The patterns of the pair of electrodes provided to the top and the bottom of the piezoelectric layer <NUM> are not limited to those shown in the first to fourth embodiments. Any suitable patterns can be employed as long as the electrode patterns provided to the top and the bottom of the piezoelectric layer <NUM> do not overlap each other in the stacking direction. It is desirable, from the viewpoint of extracting the electric charges produced at the surfaces (or the interfaces) of the piezoelectric layer <NUM>, that one charge extraction port is provided to the upper electrode, and one charge extraction port is provided to the lower electrode. The surface area of the upper electrode and the surface area of the lower electrode may be substantially the same.

In the configuration of <FIG>, the lower electrode <NUM> and the upper electrode <NUM> are staggered comb electrodes or interdigit electrodes, which alternately extend in the different layers with the piezoelectric layer <NUM> interposed therebetween. The surface area of the electrode <NUM> and the surface area of the electrode <NUM> may be substantially the same. Even if a crack runs through the piezoelectric layer <NUM> in the thickness direction due to a protrusion, a pinholes, a foreign substance, or the like that may be present on the surface of the lower electrode <NUM>, the formation of a leakage path or electrical short-circuit between the lower electrode <NUM> and the upper electrode <NUM> due to the cracking can be suppressed.

In the configuration of <FIG>, the lower electrode <NUM> and the upper electrode <NUM> are spiral electrodes which are coiled in the complementary manner at the different layers with the piezoelectric layer <NUM> interposed therebetween. The shape of the electrodes is not limited to a circular spiral as shown in <FIG>, and it may be a rectangular spiral or a polygonal spiral as long as the two electrodes do not vertically overlap each other.

The upper and the lower electrodes may be concentric electrodes that do not overlap each other although not shown in the figure. The lower electrode may have a single, a double or more annular patterns, and the upper electrode may have a single, a double or more annular patterns, each annulus being formed in the area corresponding to the space between two adjacent concentric rings of the lower electrode. The pattern is not limited to a circular ring, and may be a rectangular ring, a polygonal ring, or the like.

In the configurations of the modified embodiments, the amorphous layer <NUM> may be inserted between the substrate <NUM> and the lower electrode, as in the third and the fourth embodiments, whereby suppression of a leakage path may be further enhanced.

If a lower electrode is formed of a transparent amorphous oxide conductor on a plastic substrate <NUM>, a low-resistance amorphous film may be formed on the plastic substrate <NUM> by introducing water during the sputtering process.

The piezoelectric device having any one of the electrode structures of the present invention may be used as a piezoelectric sensor of a touch panel or the like. Even if the thickness of the piezoelectric layer can be reduced to <NUM> or less, a leakage path can be suppressed from being formed between the electrodes, and the operational reliability can be maintained.

Claim 1:
A piezoelectric device (<NUM>) comprising:
a substrate (<NUM>);
a first electrode (<NUM>, <NUM>, <NUM>, <NUM>);
a piezoelectric layer (<NUM>); and
a second electrode (<NUM>, <NUM>, <NUM>, <NUM>),
wherein the first electrode (<NUM>, <NUM>, <NUM>, <NUM>), the piezoelectric layer (<NUM>), and the second electrode (<NUM>, <NUM>, <NUM>, <NUM>) are stacked in this order on the substrate (<NUM>),
wherein the first electrode (<NUM>, <NUM>, <NUM>, <NUM>) and the second electrode (<NUM>, <NUM>, <NUM>, <NUM>) are arranged so as not to overlap each other in a stacking direction,
characterized in that the first electrode (<NUM>, <NUM>, <NUM>, <NUM>) and the second electrode (<NUM>, <NUM>, <NUM>, <NUM>) have complementary planar electrode patterns such that one of the first electrode (<NUM>, <NUM>, <NUM>, <NUM>) and the second electrode (<NUM>, <NUM>, <NUM>, <NUM>) has a shape of a cutaway of the other one of the first electrode (<NUM>, <NUM>, <NUM>, <NUM>) and the second electrode (<NUM>, <NUM>, <NUM>, <NUM>).