Acoustic wave device and fabrication method thereof

1. An acoustic wave device, comprising a substrate, as well as a first electrode layer, a piezoelectric layer and a second electrode layer which are sequentially arranged on the substrate, the acoustic wave device further comprising a protective layer,

wherein the protective layer is at least arranged at a first position above a surface, away from the substrate, of the second electrode layer; and

the first position is a position, corresponding to a first overlapping region, above the second electrode layer, and

the first overlapping region, where an active area of the acoustic wave device is located, is at least a part of a region where the first electrode layer, the second electrode layer and the piezoelectric layer are overlapped,

the acoustic wave device further comprising a conductive layer arranged on a surface, away from the substrate, of the first electrode layer and a surface, away from the substrate, of the second electrode layer,

wherein the protective layer is arranged at a position such that the protective layer does not cover the conductive layer,

wherein the protective layer comprises a first protective sublayer and a second protective sublayer;

the first protective sublayer is arranged at a position on a surface of an outermost layer away from the substrate of the acoustic wave device, such that the first protective sublayer does not cover the conductive layer;

the second protective sublayer is arranged at the first position above the surface, away from the substrate, of the second electrode layer;

the second protective sublayer is also arranged on a surface, away from the substrate, of the first protective sublayer; and

the first protective sublayer and the second protective sublayer are connected together,

wherein a position of the first protective sublayer is at a preset distance from a position of the first overlapping region,

wherein the preset distance is longer than 0.001 μm.

2. The acoustic wave device of claim 1 , wherein a region between the protective layer and a portion, corresponding to the first overlapping region, of the second electrode layer is hollow.

3. The acoustic wave device of claim 1 , wherein a region between the second protective sublayer and the second electrode layer is hollow.

4. The acoustic wave device of claim 1 , wherein the acoustic wave device further comprises a first through hole passing through the second electrode layer, the piezoelectric layer and the first electrode layer and a second through hole passing through the second protective sublayer,

wherein the second through hole is in fluid communication with the first through hole.

5. The acoustic wave device of claim 1 , wherein a thickness of the first protective sublayer ranges from 0.001 μm to 200 μm; and

a thickness of the second protective sublayer ranges from 1 μm to 200 μm.

6. A fabrication method for an acoustic wave device, comprising:

forming a substrate, and sequentially forming a first electrode layer, a piezoelectric layer and a second electrode layer on the substrate; and

forming a protective layer at least at a first position above a surface, away from the substrate, of the second electrode layer,

wherein the first position is a position, corresponding to a first overlapping region, above the second electrode layer, and

the first overlapping region, where an active area of the acoustic wave device is located, is at least a part of a region where the first electrode layer, the second electrode layer and the piezoelectric layer are overlapped,

wherein the method further comprises:

forming a conductive layer on a surface, away from the substrate, of the first electrode layer and a surface, away from the substrate, of the second electrode layer,

wherein the protective layer is formed at a position such that the protective layer does not cover the conductive layer,

wherein the protective layer comprises a first protective sublayer and a second protective sublayer, and

wherein forming the protective layer comprises:

forming the first protective sublayer at a position on a surface of an outermost layer away from the substrate of the acoustic wave device, such that the first protective sublayer does not cover the conductive layer; and

forming the second protective sublayer at the first position above the surface, away from the substrate, of the second electrode layer and on a surface, away from the substrate, of the first protective sublayer,

wherein the first protective sublayer and the second protective sublayer are connected together,

wherein forming the substrate and sequentially forming the first electrode layer, the piezoelectric layer and the second electrode layer on the substrate comprises:

forming the substrate, and sequentially forming a sacrificial layer, the first electrode layer, the piezoelectric layer and the second electrode layer on the substrate,

after forming the substrate and sequentially forming the sacrificial layer, the first electrode layer, the piezoelectric layer and the second electrode layer on the substrate, the method further comprises:

forming a first through hole passing through the second electrode layer, the piezoelectric layer and the first electrode layer; and

correspondingly, after forming the second protective sublayer, the method further comprises:

forming a second through hole passing through the second protective sublayer and in communication with the first through hole, and

removing the sacrificial layer between the first electrode layer and the substrate through the second through hole and the first through hole.

7. A fabrication method for an acoustic wave device, comprising:

forming a substrate, and sequentially forming a first electrode layer, a piezoelectric layer and a second electrode layer on the substrate; and

forming a protective layer at least at a first position above a surface, away from the substrate, of the second electrode layer,

wherein the first position is a position, corresponding to a first overlapping region, above the second electrode layer, and

the first overlapping region, where an active area of the acoustic wave device is located, is at least a part of a region where the first electrode layer, the second electrode layer and the piezoelectric layer are overlapped,

wherein the method further comprises:

forming a conductive layer on a surface, away from the substrate, of the first electrode layer and a surface, away from the substrate, of the second electrode layer,

wherein the protective layer is formed at a position such that the protective layer does not cover the conductive layer,

wherein the protective layer comprises a first protective sublayer and a second protective sublayer, and

wherein forming the protective layer comprises:

forming the first protective sublayer at a position on a surface of an outermost layer away from the substrate of the acoustic wave device, such that the first protective sublayer does not cover the conductive layer; and

forming the second protective sublayer at the first position above the surface, away from the substrate, of the second electrode layer and on a surface, away from the substrate, of the first protective sublayer,

wherein the first protective sublayer and the second protective sublayer are connected together,

wherein forming the substrate and sequentially forming the first electrode layer, the piezoelectric layer and the second electrode layer on the substrate comprises:

forming the substrate, and sequentially forming a sacrificial layer, the first electrode layer, the piezoelectric layer and the second electrode layer on the substrate,

after forming the substrate and sequentially forming the sacrificial layer, the first electrode layer, the piezoelectric layer and the second electrode layer on the substrate, the method further comprises:

forming the first through hole passing through the second electrode layer, the piezoelectric layer and the first electrode layer; and

correspondingly, before forming the second protective sublayer, the method further comprises:

removing the sacrificial layer between the first electrode layer and the substrate through the first through hole.

8. The method of claim 7 , after removing the sacrificial layer between the first electrode layer and the substrate through the first through hole, the method further comprises:

measuring a first frequency of the acoustic wave device; and

adjusting the first frequency to a second frequency on the basis of a preset frequency, wherein the second frequency is matched with the preset frequency.