Abstract: BAW resonators comprise a first electrode; a second electrode; and a piezoelectric layer disposed between the first and second electrodes. The piezoelectric layer comprises a piezoelectric material doped to a minimum atomic percentage with at least one rare earth element. In a representative embodiment, the BAW resonators comprise a first buffer layer disposed over the first electrode; and a second buffer layer disposed over the first piezoelectric layer. In a representative embodiment, the first buffer layer, or the second buffer layer, or both, are doped with the at least one rare earth element to an atomic percentage that is less than the minimum percentage.