Piezoelectric device

1. A piezoelectric device comprising:

a base portion; and

a membrane portion that is indirectly supported by the base portion, is located on an upper side relative to the base portion, and includes a plurality of layers; wherein

the membrane portion does not overlap with the base portion and includes a single crystal piezoelectric layer, an upper electrode layer provided on an upper side of the single crystal piezoelectric layer, and a lower electrode layer that faces at least a portion of the upper electrode layer with the single crystal piezoelectric layer interposed between the upper electrode layer and the lower electrode layer;

the membrane portion is provided with a through-groove penetrating in an up-down direction;

the through-groove includes a first step portion provided in a thickest layer among the plurality of layers defining the membrane portion; and

a width of the through-groove is narrower on a lower side than on an upper side with the first step portion defining a boundary.

2. The piezoelectric device according to claim 1 , wherein

the through-groove further includes a second step portion provided in any one layer of the plurality of layers defining the membrane portion above the first step portion; and

the width of the through-groove is narrower on a lower side than on an upper side with the second step portion defining a boundary.

3. The piezoelectric device according to claim 1 , wherein the width of the through-groove decreases as progressing from an upper end toward a lower end of the through-groove.

4. The piezoelectric device according to claim 1 , wherein the single crystal piezoelectric layer is made of lithium tantalate or lithium niobate.

5. The piezoelectric device according to claim 1 , wherein a portion of the single crystal piezoelectric layer extends from the membrane portion.

6. The piezoelectric device according to claim 5 , wherein the portion of the single crystal piezoelectric layer includes a hole portion that penetrates through the single crystal piezoelectric layer in the up-down direction.

7. The piezoelectric device according to claim 6 , wherein the hole portion is located above the base portion in the up-down direction.

8. The piezoelectric device according to claim 1 , wherein a close contact layer is provided between the upper electrode layer and the single crystal piezoelectric layer.

9. The piezoelectric device according to claim 5 , wherein

a portion of the lower electrode layer extends from the membrane portion; and

a close contact layer is provided between the portion of the lower electrode layer that extends from the membrane portion and the portion of the single crystal piezoelectric layer that extends from the membrane portion.

10. The piezoelectric device according to claim 1 , further comprising an intermediate layer that is in contact with a lower surface of the lower electrode layer.

11. The piezoelectric device according to claim 10 , wherein the intermediate layer is in contact with a portion of the single crystal piezoelectric layer.

12. The piezoelectric device according to claim 10 , wherein the intermediate layer includes a recessed portion.

13. The piezoelectric device according to claim 1 , further comprising:

a first outer electrode layer electrically connected to the upper electrode layer; and

a second outer electrode layer electrically connected to the lower electrode layer.

14. The piezoelectric device according to claim 1 , wherein the single crystal piezoelectric layer performs bending vibration in response to a voltage applied between the upper electrode layer and the lower electrode layer.