To provide a thin semiconductor device which can prevent deterioration in the reliability by a heavy metal contamination in a sealing step with a resin, etc.

The semiconductor device has a semiconductor integrated circuit in an upper part; and a semiconductor substrate 1, formed in advance in an interior with a minute defective layer 2, is thinned from the rear surface of the substrate by 150 μm or smaller in thickness, so that it may leave minute defective layer 2.