Abstract: The invention discloses a bulk acoustic wave resonator and a manufacturing method thereof, the bulk acoustic wave resonator comprising: an air gap arranged at the external of the effective piezoelectric region, the air gap being formed between the upper electrode and the piezoelectric layer and/or between the piezoelectric layer and the substrate, and covering the end part, proximal to the air gap, of the lower electrode or connecting to the end part of the lower electrode, wherein the air gap is provided with a first end proximal to the effective piezoelectric region, and at least a portion of the upper surface, starting from the first end, of the air gap is an arch-shaped upper surface. The bulk acoustic wave resonator of the present invention capable of increasing a quality factor (Q) and an effective electromechanical coupling coefficient (K2t,eff) and improving the electrostatic discharge (ESD) immunity.

Abstract: A wideband piezoelectric filter with a ladder-type is provided, which is composed of a plurality of first resonators connected in series, a plurality of second resonators connected in parallel, an impedance matching device disposed near the input terminal or the output terminal of the filter, and at least one special parallel ground path led out from serial nodes. The special parallel ground path at least comprises one inductor having a larger inductance value, and a resonator having the same resonant frequency as a serial branch or a capacitor, wherein the larger inductor is connected to the resonator or capacitor in series in the parallel path. The ladder filter according to the invention can have a bandwidth which is more than twice that of the conventional ladder filter, and also has excellent out-of-band rejection characteristics.