BAW resonator with a high Q value and interference mode suppression

摘要

A BAW resonator is provided, the upper electrode having an outer flap. The flap extends from the active resonator region and has a protruding portion that extends at a level above the piezoelectric layer that is higher than the level of the top electrode in any of the interior regions enclosed by the outer flap. The higher level is formed by an inserted step-forming material, which is arranged between the piezoelectric layer and the upper electrode in the outer flap. The step-forming material comprises a structured layer with an acoustic impedance that is low in relation to the impedance of the upper electrode and the piezoelectric layer.