| 摘要 |
PROBLEM TO BE SOLVED: To provide a piezoelectric thin film resonator with excellent mechanical strength, mountability, reliability and productivity and having excellent piezoelectric film orientation, and to provide a filter and a manufacturing method of them. SOLUTION: An air gap 42 with a dome shaped swelling is formed between a substrate 41 and a lower side of a lower electrode 43 in a region (membrane part 46) wherein the upper electrode 45 and the lower electrode 43 are opposed to each other. Then the air gap 42 has a contour whose projected shape to the substrate 41 is a closed curve. Further, the substrate 41 is provided with an etching liquid introduction hole 47 for sacrifice layer etching to etch the sacrifice layer for forming the air gap 42. The etching of the sacrifice layer 48 is executed such that a stress of a laminated body (composite film) comprising a piezoelectric film 44 and the upper electrode 45 is a compressive stress, the composite film is swollen, and the dome shaped air gap 42 can be formed between the lower electrode 43 and the substrate 41. COPYRIGHT: (C)2006,JPO&NCIPI
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