BULK ACOUSTIC WAVE RESONATOR USING ACOUSTIC REFLECTOR LAYERS AS INDUCTIVE OR CAPACITIVE CIRCUIT ELEMENT

摘要

A resonator comprises a bottom electrode layer (12), a top electrode layer (14) and a piezoelectric layer (10) sandwiched between the top and bottom electrode layers. A multi-layer acoustic reflector (16) is provided beneath the bottom electrode layer. The external electrical connections to the resonator comprise a first electrical connection to the top or bottom electrode layer and a second electrical connection to one of the layers of the acoustic reflector (16). The multi-layer acoustic reflector layers can define at least one circuit element in the form of a capacitor or inductor which forms part of the resonator circuit. Alternatively, the electrical connections can be used to define a resonator operating at a different frequency. This arrangement makes use of the layers of the reflector to provide additional circuit functions, including an inductor and/or capacitor, or to change the frequency characteristics. This enables additional circuit elements to be defined in an integrated way and without using additional substrate area.