Patent ID: 8704378

Claim:
A semiconductor device, comprising: a first substrate on which a first semiconductor chip is mounted; a second substrate on which a second semiconductor chip is mounted; and connecting sections that contact the front surface of said first substrate and the back surface of said second substrate, and electrically connect said first substrate and said second substrate; wherein said first substrate has a build-up layer in which insulating layers containing a resin and conductor interconnect layers are laminated alternately, and said each conductor interconnect layer is connected by a conductive layer provided in a hole of said insulating layer, said second substrate has build-up layer in which insulating layers containing a resin and conductor interconnect layers are laminated alternately, and said each conductor interconnect layer is connected by a conductive layer arranged in a hole of said insulating layer, among the insulating layers of said build-up layer in at least one substrate of said first substrate and said second substrate, in at least one insulating layer, the average coefficient of thermal expansion along the substrate inplane direction at from 25 degrees centigrade to the glass transition point is 30 ppm/degrees centigrade or less, and the average coefficient of thermal expansion along the substrate thickness direction at from 25 degrees centigrade to the glass transition point is 30 ppm/degrees centigrade or less, at least one substrate of said first substrate and said second substrates has a core layer wherein a through-hole provided with a conductive layer is formed in the inside of an insulating layer, and said conductive layer in the through-hole is connected to said conductor interconnect layer of said built-up layer, and the core layer contains a resin and a glass fiber, and wherein the average coefficient of thermal expansion along the substrate inplane direction of said insulating layer of said core layer at 25 degrees centigrade to the glass transition point is 12 ppm/degrees centigrade or less, and the average coefficient of thermal expansion along the substrate thickness direction of said insulating layer of said core layer at 25 degrees centigrade to the glass transition point is 20 ppm/degrees centigrade or less, the average coefficient of thermal expansion along the substrate inplane direction of said insulating layer of said core layer at from 25 degrees centigrade to the glass transition point is lower than that of said build-up layer, and the average coefficient of thermal expansion along the substrate thickness direction of said insulating layer of said core layer at from 25 degrees centigrade to the glass transition point is lower than that of said build-up layer, whereby the core layer serves to reduce the coefficient of thermal expansion of the first and second substrates.