A semiconductor substrate adapted to giga-scale integration (GSI) comprises a support, at least the surface of which is made of semiconductor, an electroconductive material layer, an insulating layer and a semiconductor layer arranged sequentially in the above order. The electroconductive material layer has at least in part thereof an electroconductive reacted layer obtained by causing two metals, a metal and a semiconductor, a metal and a metal-semiconductor compound, a semiconductor and a metal-semiconductor compound, or two metal-semiconductor compounds to react each other. An electroconductive reaction terminating layer that is made of a material that does not react with the reacted layer is arranged between the reacted layer and the insulating layer or the support.