PURPOSE: To form a semiconductor substrate which is formed as a single crystal semiconductor layer on a dielectric separating or insulating substance and suitable for electronic devices and integrated circuits.

CONSTITUTION: A semiconductor substrate having a single crystal silicon layer is formed on a light transmissive base material by forming a single crystal silicon layer on a porous silicon substrate by epitaxial growth and performing an oxidation process. For forming the crystalline silicon layer having an excellent crystallinity equivalent to that of the transparent base material (light transmissive base material), a method which is excellent in productivity, uniformity, controllability, and economy can be provided. In addition, an excellent single crystal silicon thin film can be formed on the light transmissive base material by efficiently reducing the occurrence of defects in the single crystal silicon layer having the excellent crystallinity.