Acoustic wave device including a surface wave filter and a bulk wave filter, and method for making same

A method for fabricating an acoustic wave device comprising at least one surface acoustic wave filter and at least one bulk acoustic wave filter, the method comprising:

• forming a first stack comprising at least one layer of piezoelectric material, a first metal layer disposed on a surface of the at least one layer of piezoelectric material, and a layer of a first monocrystalline piezoelectric material completely over the first metal layer by applying the layer of the first monocrystalline piezoelectric material covered by the first metal layer, on the at least one layer of piezoelectric material;
• forming a second area by partially etching said first stack so that the first monocrystalline piezoelectric material is absent;
• producing a second metal layer over the layer of the first monocrystalline piezoelectric material in the first stack, the first stack defining the at least one bulk acoustic wave filter incorporating the first monocrystalline piezoelectric material;
• and
• producing a third metal layer over the at least one layer of the at least one layer of piezoelectric material in the second area, the second area defining the at least one surface acoustic wave filter incorporating the at least one layer of piezoelectric material.