Sumitomo Electric Industries, Limited

Keiichiro Geshi

Shigeru Nakayama

Masashi Yoshimura

Hirohisa Saito

Yuichiro Yamanaka

Yoshihiro Imagawa

Provided is a joined body including a piezoelectric substrate and a polycrystalline spinel substrate provided on one main surface of the piezoelectric substrate, wherein the polycrystalline spinel substrate has a porosity of 0.005% or more and 0.6% or less.

Joined body and surface acoustic wave device

Provided is a polycrystalline ceramic substrate to be bonded to a compound semiconductor substrate with a bonding layer interposed therebetween, wherein at least one of relational expression (1) 0.7&#x3c;&#x3b1;/&#x3b1;&#x3c;0.9 and relational expression (2) 0.7&#x3c;&#x3b1;/&#x3b1;&#x3c;0.9 holds, where &#x3b1;represents a linear expansion coefficient of the polycrystalline ceramic substrate at 30&#xb0; C. to 300&#xb0; C. and &#x3b1;represents a linear expansion coefficient of the compound semiconductor substrate at 30&#xb0; C. to 300&#xb0; C., and &#x3b1;represents a linear expansion coefficient of the polycrystalline ceramic substrate at 30&#xb0; C. to 1000&#xb0; C. and &#x3b1;represents a linear expansion coefficient of the compound semiconductor substrate at 30&#xb0; C. to 1000&#xb0; C.

Polycrystalline ceramic substrate, bonding-layer-including polycrystalline ceramic substrate, and laminated substrate

A ceramic substrate is formed of a polycrystalline ceramic and has a supporting main surface. The supporting main surface has a roughness of 0.01 nm or more and 3.0 nm or less in terms of Sa. The number of projections and depressions with a height of 1 nm or more in a square region with 50 &#x3bc;m sides on the supporting main surface is less than 5 on average, and the number of projections and depressions with a height of 2 nm or more in the square region is less than 1 on average.

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Osaka, Japan

Keiichiro Geshi