Patent ID: 7396733

Claim:
A method for manufacturing a semiconductor substrate, comprising: forming a first semiconductor layer on a semiconductive base; forming a second semiconductor layer, having a smaller etching selection ratio than that of the first semiconductor layer, on the first semiconductor layer; removing part of the first semiconductor layer and the second semiconductor layer in the vicinity of device region, so as to form a support hole that exposes the semiconductive base; forming a support forming layer on the semiconductive base, so that the support hole is buried and the second semiconductor layer is covered; leaving an region that includes the support hole and the element region, etching the rest, so that an exposed surface is formed, where a part of edges of a support, the first semiconductor layer, and of the second semiconductor layer located at the lower side of the support are exposed; forming a cavity between the second semiconductor layer and the semiconductive base by etching the first semiconductor layer through the exposed surface; forming a buried insulation layer inside the cavity; and planarizing the top side of the second semiconductor layer and removing the part of the support above the second semiconductor layer; wherein, in forming the first semiconductor layer, the first semiconductor layer is deposited with a first condition on a first region where an oxide film does not exist on the semiconductive base.