Process for preparation of semiconductor devices utilizing a two-step

Abstract

A semiconductor substrate having a single crystal semiconductor layer of one conductivity type exposed to the surface thereof is maintained at a temperature lower than the temperature at which the semiconductors is precipitated from the gas phase. In this state, a gas of a starting material of a semiconductor, a gas containing impurities capable of forming a semiconductor of the other conductivity type and a carrier gas therefore are fed onto the semiconductor substrate. Then, the semiconductor substrate is heated to form an amorphous or polycrystalline semiconductor layer of the other conductivity type on the semiconductor substrate. Simultaneously, the impurities of the other conductivity type are diffused from the amorphous or polycrystal semiconductor layer into the substrate which has a single crystal semiconductor layer of one conductivity type, to form a single crystal semiconductor layer having a p-n junction just below the amorphous or polycrystal semiconductor layer between the amorphous or polycrystalline semiconductor layer and the single crystal semiconductor layer of one conductivity type. In a p-n junction to be formed according to this process, the distribution of the concentration of impurities can be controlled precisely, and the step-like distribution of the concentration of impurities can be attained very well.