Patent ID: 7790271

Claim:
A ceramic substrate having a laminated structure comprising: outer layer portions and an inner layer portion, the outer layer portions and the inner layer portion including a SiO 2 -based crystal phase, a content of the SiO 2 -based crystal phase being less in the outer layer portions than in the inner layer portion so that the outer layer portions have a smaller thermal expansion coefficient than the inner layer portion; wherein the outer layer portion includes a dielectric ceramic composition comprising about 10% to about 40% by weight of BaO, about 20% to about 65% by weight of SiO 2 , about 6% to about 40% by weight of Al 2 O 3 , about 1% to about 15% by weight of B 2 O 3 , about 0.3% to about 3% by weight of Cr 2 O 3 , and about 1% to about 40% by weight of ZrO 2 , the dielectric ceramic composition being sintered; and the inner layer portion is made of materials having substantially the same composition as materials of the outer layer portions except for the content of the SiO 2 -based crystal phase, and the inner layer portion includes substantially no zirconium.