A film bulk acoustic wave resonator includes a first substrate; a first insulating material layer, formed on the first substrate; a first cavity, formed in the first insulating material layer with an opening facing away from the first substrate; and an acoustic-wave resonant plate, including a first electrode, a piezoelectric oscillation plate, and a second electrode stacked on the first insulating material layer. The piezoelectric oscillation plate is disposed between the first electrode and the first electrode. The first electrode includes a first electrode cavity above the first cavity. The second electrode includes a second cavity above the first cavity. At least a portion of a boundary of the piezoelectric oscillation plate is formed by a boundary of the first electrode cavity and a boundary of the second electrode cavity. The boundary of the piezoelectric oscillation plate has an irregular polygonal shape without having two parallel edges.