| abstract |
A pit ( 52 ) is formed in a substrate comprising a silicon wafer ( 51 ) on a surface of which a silicon oxide thin layer ( 53 ) is formed. A sandwich structure ( 60 ) comprising a piezoelectric layer ( 62 ) and lower and upper electrodes ( 61, 63 ) joined to both surfaces of the piezoelectric layer is disposed so as to stride over the pit ( 52 ). The upper surface of the lower electrode ( 61 ) and the lower surface of the piezoelectric layer ( 62 ) joined to the upper surface of the lower electrode are treated so that the RMS variation of the height thereof is equal to 25 nm or less. The thickness of the lower electrode ( 61 ) is set to 150 nm or less. According to such a structure, there is provided a high-performance thin film bulk acoustic resonator which are excellent in electromechanical coupling coefficient and acoustic quality factor. |