Composite substrate and its manufacturing method and elastic surface wave element

Abstract

A composite substrate with excellent bonding strength and simple, low-cost manufacturing capability is provided. According to an embodiment of the present invention, the composite substrate sequentially comprises a piezoelectric layer, a first intermediate layer, a second intermediate layer, and a support substrate. The resistivity R21 of the first intermediate layer side of the second intermediate layer is higher than the resistivity RS of the support substrate; and the resistivity R2S of the support substrate side of the second intermediate layer is lower than the resistivity RS of the support substrate. A method for manufacturing the composite substrate according to an embodiment of the present invention sequentially includes: forming a first intermediate layer and a second intermediate layer sequentially on one side of the piezoelectric substrate; smoothing the second intermediate layer; bonding the second intermediate layer to the support substrate; and thinning the piezoelectric substrate to form a piezoelectric layer; the first intermediate layer is formed by reactive sputtering of silicon in the presence of oxygen; and the second intermediate layer is formed by reactive sputtering of silicon in an environment with a residual oxygen content below that used for the formation of the first intermediate layer.

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