High definition anodized sublayer boundary.

摘要

A semiconductor structure has a high definition boundary between semiconductor islands (54) and an isolating sublayer (50) having a transition thickness less than 1500A. To form the structure a trench (62) is formed in a composite epitaxial layer (54) and an N<+> sublayer (50). The sublayer (50) is anodized and oxidized at a high pressure and low temperature environment, reducing updiffusion of the N<+> impurities into the epitaxial layer (54).