Patent ID: 8729771
Filing Date: 2014-05-20
Classification: H01L,H03H,Y10T

Abstract:
1. A composite substrate comprising: a piezoelectric substrate having asperities formed in one surface thereof; a support substrate having a smaller thermal expansion coefficient than the piezoelectric substrate; a filling layer formed to fill the asperities and having a joined surface on the side oppositely away from the piezoelectric substrate, the joined surface having an arithmetic mean roughness Ra smaller than an arithmetic mean roughness Ra of the one surface of the piezoelectric substrate; and an adhesive layer bonding the joined surface and the support substrate to each other, wherein a first boundary exists between the adhesive layer and the filling layer, and no bubbles are present at the first boundary between the adhesive layer and the filling layer, inside the adhesive layer, and at a second boundary between the adhesive layer and the support substrate.