摘要 |
PURPOSE:To prevent inversion of a burried SiO2 and an Si substrate interface by restraining segregation of B by a method wherein an acid resistive thin film is formed on the bottom surface of the burried SiO2 separating layer on the Si substrate. CONSTITUTION:An epitaxial layer 23 is formed on the P type Si substrate 21 on which an N layer 22 selectively is mounted. Burried SiO2 24-24'' approximately equivalent to the layer 23 in thickness are provided, the epiraxial layer is separated and circuit elements 25, 25' are formed. Si3N4 layers 27-27'' are formed on the bottom surface of the SiO2 24-24'' to prevent to SiO2 from being grown and at the same time, to restrain the segregation of B at heat treating and to prevent the surface of P type Si substrate from being inverted to an N type. Accordingly, a phenomenon in which separated islands are electrically connected with each other will not occur nor the circuit function is broken. |