PURPOSE: To provide a semiconductor substrate which is subjected to electrochemical etching by which especially a small thickness part is processed with a high precision.

CONSTITUTION: An N-type semiconductor layer 13 is formed on the surface of a P-type semiconductor wafer 12 to form a semiconductor substrate 11. A separation belt 15 is formed in the semiconductor layer 13 so as to mark off a chip arranging region 14 from an outer circumferential region 141 surrounding the region 14. The separation belt 15 is formed by filling a trench which is formed so as to reach the surface of the P-type semiconductor wafer 12 from the surface of the semiconductor layer 13 by etching with dielectric material. That is, the outer circumferential region 14 in which current leakage generating parts 19 such as defective parts of P-N junctions exist is electrically separated from the chip arranging region 14 by the separation belt 15 and the generation of leakage currents from P-N junctions in the chip arranging region 14 can be avoided.