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A method of fabricating a rare-earth element doped piezoelectric material having a first component, a second component and the rare-earth element. The method includes: providing a substrate; initially flowing hydrogen over the substrate; after the initially flowing of the hydrogen over the substrate

A method of fabricating a rare-earth element doped piezoelectric material having a first component, a second component and the rare-earth element. The method includes: providing a substrate; initially flowing hydrogen over the substrate; after the initially flowing of the hydrogen over the substrate, flowing the first component to form the rare-earth element doped piezoelectric material over a surface of a target, the target comprising the rare-earth metal in a certain atomic percentage; and sputtering the rare-earth element doped piezoelectric material from the target on the substrate.

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1. A BAW resonator, comprising: a first electrode disposed over a substrate;an electropositive seed layer comprising aluminum and scandium (Al—Sc), and disposed over the substrate;a piezoelectric layer disposed over the electropositive seed layer and comprising a rare-earth element doped piezoelectr

1. A BAW resonator, comprising: a first electrode disposed over a substrate;an electropositive seed layer comprising aluminum and scandium (Al—Sc), and disposed over the substrate;a piezoelectric layer disposed over the electropositive seed layer and comprising a rare-earth element doped piezoelectric material having a compression-negative (CN) polarity, wherein the electropositive seed layer fosters growth of the piezoelectric layer having the compression-negative (CN) polarity; anda second electrode disposed over the rare-earth element doped piezoelectric material. 2. A BAW resonator as claimed in claim 1, wherein the rare-earth element doped piezoelectric material comprises a first component and a second component. 3. A BAW resonator as claimed in claim 2, wherein the rare-earth element is scandium (Sc), the first component is nitrogen (N), and the second component is aluminum (Al). 4. A bulk acoustic wave (BAW) resonator structure, comprising: a first electrode disposed over a substrate;a first non-ferroelectric piezoelectric layer disposed over the first electrode, the first non-ferroelectric piezoelectric layer having a first c-axis oriented along a first direction, and comprising a rare-earth element doped non-ferroelectric piezoelectric material;a second electrode disposed over the first non-ferroelectric piezoelectric layer;a second non-ferroelectric piezoelectric layer disposed over the first electrode, the second non-ferroelectric piezoelectric layer being adjacent to, and in direct contact with, the first non-ferroelectric piezoelectric layer, wherein the second non-ferroelectric piezoelectric layer has a second c-axis oriented in a second direction that is substantially antiparallel to the first direction; andan acoustic reflector disposed in the substrate. 5. A BAW resonator structure as claimed in claim 4, wherein the second non-ferroelectric piezoelectric layer comprises the rare-earth element doped non-ferroelectric piezoelectric material. 6. A BAW resonator structure as claimed in claim 5, wherein the second non-ferroelectric piezoelectric layer has a piezoelectric coupling coefficient (e33ip) that is substantially equal in magnitude but opposite in sign to a piezoelectric coupling coefficient (e33p) of the first non-ferroelectric piezoelectric layer. 7. A BAW resonator structure as claimed in claim 5, wherein the rare-earth element doped non-ferroelectric material comprises scandium doped aluminum nitride (AlScN). 8. A bulk acoustic wave (BAW) resonator structure, comprising: a first electrode disposed over a substrate;a cavity beneath the first electrode;a first non-ferroelectric piezoelectric layer disposed over the first electrode, the first non-electric piezoelectric layer comprising a rare-earth element doped non-ferroelectric piezoelectric material, and having a first c-axis oriented along a first direction;a second electrode disposed over the first non-ferroelectric piezoelectric layer, wherein an active region of the BAW resonator structure comprises an overlap of the first electrode and the second electrode with the cavity; anda second non-ferroelectric piezoelectric layer disposed over the first electrode, the second non-ferroelectric piezoelectric layer being adjacent to, and in direct contact with, the first non-ferroelectric piezoelectric layer, the second non-ferroelectric piezoelectric layer having a second c-axis oriented in a second direction that is substantially antiparallel to the first direction, wherein the second electrode overlaps the second non-ferroelectric piezoelectric layer; andan acoustic reflector disposed in the substrate. 9. A BAW resonator structure as claimed in claim 8, wherein the first non-ferroelectric piezoelectric layer comprises the rare-earth element doped non-ferroelectric piezoelectric material, or the second non-ferroelectric piezoelectric layer comprises the rare-earth element doped non-ferroelectric piezoelectric material, or both. 10. A BAW resonator structure as claimed in claim 9, wherein the second non-ferroelectric piezoelectric layer has a piezoelectric coupling coefficient (e33ip) that is substantially equal in magnitude but opposite in sign of a piezoelectric coupling coefficient (e33p) of the first non-ferroelectric piezoelectric layer. 11. A BAW resonator structure as claimed in claim 9, wherein the rare-earth element doped non-ferroelectric piezoelectric material comprises scandium doped aluminum nitride (AlScN). 12. A BAW resonator as claimed in claim 1, wherein the electropositive seed layer is comparatively pure. 13. A BAW resonator as claimed in claim 1, wherein the electropositive seed layer is disposed directly on an upper surface of the first electrode. 14. A BAW resonator as claimed in claim 1, wherein a thickness of the electropositive seed layer is in a range of approximately 50 {acute over (Å)} to approximately 1000 {acute over (Å)}. 15. A BAW resonator as claimed in claim 2, wherein a thickness wherein a thickness of the electropositive seed layer is in a range of approximately 50 {acute over (Å)} to approximately 1000 {acute over (Å)}. 16. A BAW resonator as claimed in claim 7, wherein atomic percentage of scandium in the scandium doped aluminum nitride (AlScN) is approximately 0.5% to approximately 44%. 17. A BAW resonator as claimed in claim 7, wherein atomic percentage of scandium in the scandium doped aluminum nitride (AlScN) is approximately 2.5% to approximately 5%. 18. A BAW resonator as claimed in claim 7, wherein atomic percentage of scandium in the scandium doped aluminum nitride (AlScN) is approximately 0.5% to less than approximately 10.0%. 19. A BAW resonator as claimed in claim 11, wherein atomic percentage of scandium in the scandium doped aluminum nitride (AlScN) is approximately 0.5% to approximately 44%. 20. A BAW resonator as claimed in claim 11, wherein atomic percentage of scandium in the scandium doped aluminum nitride (AlScN) is approximately 2.5% to approximately 5%. 21. A BAW resonator as claimed in claim 11, wherein atomic percentage of scandium in the scandium doped aluminum nitride (AlScN) is approximately 0.5% to less than approximately 10.0%.