| 摘要 |
In a composite substrate 10, a bonding surface 21 of a piezoelectric substrate 20 is an irregular surface which is partially planarized. The irregular surface which is partially planarized includes a plurality of protrusions 23, each having a flat portion 25 on the tip thereof. The piezoelectric substrate 20 and the supporting substrate 30 are directly bonded to each other at the flat portions 25. By forming the bonding surface 21 into an irregular surface (rough surface) and providing flat portions 25 at the same time, it is possible to secure a sufficient contact area between the piezoelectric substrate 20 and the supporting substrate 30. Accordingly, in the composite substrate in which the piezoelectric substrate 20 and the supporting substrate 30 are bonded to each other, the bonding surface 21 can be roughened and direct bonding can be performed. Furthermore, it is possible to obtain a surface acoustic wave device in which heat resistance is enhanced by performing direct bonding without using an adhesive, and also bulk waves are scattered because of the roughened bonding surface, thus improving characteristics. |
