substrate 100 has a large heat discharge characteristic since the cooling silicon substrate 100 is formed independently of the integrated circuit silicon substrate 3 the height th of the cooling silicon substrate 100 can be determined freely independently of the height tc of the integrated circuit silicon substrate 3 when a yield on forming the integrated circuit silicon substrate 3 is a a yield on forming the cooling silicon substrate 100 is b and a yield on joining the integrated circuit silicon substrate 3 and the cooling silicon substrate 100 is c a yield y1 on forming both the integrated circuit and the cooling fins 1 on one or the identical substrate without the joining is a b a yield y2 on forming the integrated circuit and the cooling fins 1 on respective substrates and subsequently joining the substrates is a c because a lt b generally since b lt c generally y1 lt y2 therefore the present invention brings about an advantageous effect when a base component of the integrated circuit silicon substrate 3 for example silicon is equal to that of the cooling silicon substrate 100 for making a thermal expansion coefficiency of the integrated circuit silicon substrate 3 equal to that of the cooling silicon substrate 100 a stress caused by a difference in thermal expansion coefficiency therebetween is prevented a purity of the base component of.