PURPOSE: To manufacture a semiconductor device of a high yield by preventing the film peeling at an outer part of a semiconductor substrate and then by providing a very reliable semiconductor substrate.

CONSTITUTION: In a semiconductor substrate wherein an insulating film 102 and a semiconductor layer 103 are deposited in this order on a supporting substrate 101, an outer part of at least the insulating film 102 is coated with a protective film 104 which is constituted of an insulating film or a semiconductor layer. The protective film 104 is a semiconductor film made of polycrystalline silicon. Since the outer part of the insulating film 102 is protected with the protective film 104, the outer part of the insulating film 102 is never etched when the substrate is etched in a post-process and therefore the lift-off or exfoliation of the semiconductor layer 103 can be avoided.