Patent ID: 8853089

Claim:
A manufacturing method of a semiconductor substrate comprising: forming a trench in a semiconductor board by a dry etching method; etching a surface portion of an inner wall of the trench by a chemical etching method so that a first damage layer is removed, wherein the surface portion has a thickness equal to or larger than 50 nanometers; and performing a heat treatment at temperature equal to or higher than 1050° C. in non-oxidizing and non-azotizing gas so that crystallinity of a second damage layer is recovered, wherein the second damage layer is disposed under the first damage layer, wherein crystallinity of the first damage layer is not recovered by the heat treatment, the second damage layer is disposed further from the inner wall of the trench than the first damage layer, the etching of the surface portion is performed after the forming of the trench, and the performing of the heat treatment is performed after the etching of the surface portion.