Bulk acoustic wave resonator device e.g. thin film bulk acoustic resonator device, for ladder filter for e.g. laptops, has compensation layer including positive temperature coefficient for offsetting portion of negative coefficient

摘要

The device e.g. thin film bulk acoustic wave resonator device (200), has a bottom electrode (220) placed on a substrate (110) over a cavity (115) or acoustic mirror. A piezoelectric layer (130) is formed on the electrode. A top electrode is placed on the piezoelectric layer. A temperature compensation feature or layer (227) defines positive temperature coefficient for offsetting a portion of negative temperature coefficient of the piezoelectric layer, where the bottom or top electrode comprises an integrated lateral feature to create cut-off frequency mismatch or acoustic impedance mismatch. The acoustic mirror is a Bragg mirror. The substrate is formed of semiconductor material e.g. silicon, gallium arsenide, indium phosphide, glass, sapphire and alumina.