Bulk acoustic wave resonator device

A bulk acoustic wave resonator device, comprising:

• a substrate;
• a first layer disposed on the substrate and forming a cavity together with the substrate;
• a lower electrode disposed on the first layer;
• a piezoelectric layer covering a portion of the lower electrode;
• an upper electrode disposed on the piezoelectric layer;
• a protective layer covering a portion of the upper electrode;
• and
• a shape control layer disposed over an edge of the cavity,
• wherein tensile stress is applied to the shape control layer during formation of the shape control layer, and
• residual stress remains in the shape control layer.

A bulk acoustic wave resonator device, comprising:

• a first layer disposed on a substrate, wherein a cavity is disposed between the substrate and the first layer;
• a lower electrode disposed on a portion of the first layer that covers the cavity in part;
• a piezoelectric layer disposed on a portion of the lower electrode;
• an upper electrode formed on the piezoelectric layer;
• and
• a shape control layer configured to cover a portion of the lower electrode at an end portion of the cavity and cover a portion of the upper electrode at another end portion of the cavity, wherein tensile stress is applied to the shape control layer during formation of the shape control layer.