Method of manufacturing a piezoelectric acoustic wave device

A method of manufacturing a frequency thickness resonant mode piezoelectric acoustic wave device, said device comprising a piezoelectric plate having a top surface and a bottom surface, a substrate having a top surface and a bottom surface, and exciting electrodes, said exciting electrodes contacting and exciting a resonating part of said piezoelectric plate, comprising:

• digging into at least one of said substrate and said piezoelectric plate to form a depression having an area larger than the area of said resonating part of said piezoelectric plate;
• bonding the top surface of said substrate and the bottom surface of said piezoelectric plate around said depression by chemical treatment without an adhesive with said resonating part overlying said depression;
• introducing an intermediate support material into said depression to form an intermediate support layer which supports and fixes said resonating part of said piezoelectric plate relative to said substrate;
• thinning at least said resonating part of said piezoelectric plate;
• and
• removing said intermediate support material after said thinning step.