Patent ID: 7388293

Claim:
An interposer to be interposed between a semiconductor chip to be mounted thereon and a packaging board, the interposer comprising: a first interposer portion formed of a first material having a thermal expansion coefficient equivalent to that of the semiconductor chip to be mounted thereon; a second interposer portion formed of a second material different from said first material and provided around the first interposer portion integrally therewith, both upper and lower surfaces of the second interposer portion being on a level with those of the first interposer position; and insulating layers formed on both upper and lower surfaces of the first and second interposer portions, wherein wiring patterns are formed on said insulating layers, and are electrically connected via through holes formed at required positions in the first and second interposer portions, and wherein the first interposer portion has a size approximately equal to that of the semiconductor chip to be mounted thereon.