BONDED SUBSTRATE, METHOD FOR PRODUCING SAME AND SURFACE ACOUSTIC WAVE DEVICE USING SAID BONDED SUBSTRATE

摘要

[Problem] The purpose of the present invention is to provide a bonded substrate which has excellent temperature characteristics and is suppressed in terms of unnecessary responses due to reflection of acoustic waves at the bonding interface. [Solution] The present invention is characterized in that: this bonded substrate is configured by bonding an LiTaO3 substrate and a base substrate; and the Li concentration of the LiTaO3 substrate in the bonded surface that is in contact with the base substrate is higher than the Li concentration in the LiTaO3 substrate-side surface of the bonded substrate. In addition, it is preferable that the difference between the Li concentration of the LiTaO3 substrate in the bonded surface that is in contact with the base substrate and the Li concentration in the LiTaO3 substrate-side surface of the bonded substrate is 0.1 mol% or more; the Li concentration of the LiTaO3 substrate in the bonded surface that is in contact with the base substrate is expressed by Li/(Li + Ta) × 100 = (50 + α) mol% wherein α is within the range of -1.2 < α < 0.5; the Li concentration in the LiTaO3 substrate-side surface of the bonded substrate is expressed by Li/(Li + Ta) × 100 = (48.5 + β) mol% wherein β is within the range of -0.5 < β < 0.5; and the thickness from the bonding interface between the LiTaO3 substrate and the base substrate to the LiTaO3 substrate-side surface is more than 5 times but less than 20 times the wavelength of surface acoustic waves or leakage surface acoustic waves.