Acoustic bandgap structures adapted to suppress parasitic resonances in tunable ferroelectric capacitors and method of operation and fabrication therefore

1. An apparatus, comprising:

a stack of at least three ferroelectric layers with a top side and bottom side of each of said ferroelectric layers contacting an electrode layer;

wherein said ferroelectric layers and said electrode layers form a substantially periodic structure in the direction normal to said ferroelectric and electrode layers;

wherein an acoustic characteristic impedance and thickness of each layer are selected to realize an acoustic bandgap over a desired frequency band; and

wherein a subset of the electrode and ferroelectric layers are rendered acoustically inert by shorting the electrode layers.

2. The apparatus of claim 1 , wherein all ferroelectric layers except for one layer are rendered acoustically inert by electrically shorting the electrodes on opposite sides of a given ferroelectric layer.

3. The apparatus of claim 2 , wherein said electrically shorting is accomplished by conductive vias.

4. The apparatus of claim 1 , wherein all ferroelectric layers except for two layers are rendered acoustically inert by electrically shorting the electrodes on opposite sides of a given ferroelectric layer.

5. The apparatus of claim 1 , wherein said electrodes are metal layers and wherein said metal layers have essentially the same acoustic characteristic impedance and the same thickness.

6. The apparatus of claim 1 , wherein said ferroelectric layers have essentially the same acoustic characteristic impedance and the same thickness.

7. The apparatus of claim 1 , wherein said electrode layers are each comprised of multiple sublayers.

8. The apparatus of claim 1 , further comprising at least one additional passivation layer and at least one final metal interconnect layers used for wire bonding or flip-chip attachment to the next level of assembly.

9. A tunable ferroelectric capacitor, comprising:

a multilayer one dimensional periodic structure containing multiple unit cells, wherein each unit cell contains a plurality of ferroelectric layers with layers of low and high acoustic characteristic impedance;

wherein the acoustic impedances of individual layers in said unit cells are selected to produce an acoustic bandgap for a desired frequency band; and

wherein a subset of electrode layers and the ferroelectric layers are rendered acoustically inert by shorting the electrode layers.

10. The tunable ferroelectric capacitor of claim 9 , wherein at least one of said plurality of ferroelectric layers is contacted on both sides by conductive electrode layers.

11. The tunable ferroelectric capacitor of claim 9 , wherein all the ferroelectric layers except for one or two layers are rendered acoustically inert.

12. The tunable ferroelectric capacitor of claim 11 , wherein said electrically shorting is accomplished by conductive vias.

13. The tunable ferroelectric capacitor of claim 10 , wherein said electrodes are metal layers and wherein said metal layers have essentially the same acoustic characteristic impedance and the same thickness.

14. The tunable ferroelectric capacitor of claim 9 , wherein said plurality of ferroelectric layers have essentially the same acoustic characteristic impedance and the same thickness.

15. The tunable ferroelectric capacitor of claim 9 , wherein said electrode layers are each comprised of multiple sublayers.

16. The tunable ferroelectric capacitor of claim 9 , further comprising at least one additional passivation layer and at least one final metal interconnect layer used for wire bonding or flip-chip attachment to the next level of assembly.