SOI STRUCTURE FOR BICMOS INTEGRATED CIRCUIT

摘要

PURPOSE: To form a BiCMOS structure on a bonded SOI wafer by a method, wherein a deep SOI region and a shallow SOI region are formed simultaneously on a same substrate, and the deep region is used for the bipolar structure and the shallow region is used for the BiCMOS structure. CONSTITUTION: Trenches are formed in a bulk silicon wafer 10 for defining a region to be a relatively shallow semiconductor region and a relatively deep region in a final structure. A resist layer 14 of an initial pattern is formed and etched through an aperture 23. An aperture is formed in a layer 12 by etching to form trench segments. In order to form a deep trench, the aperture 23 is enlarged by the pattern and the deep trench is formed by etching. A stepped trench which has a trench segment 22 started first and a trench segment 24 started eater are formed. An SOI structure which has a deep silicon region 38 is formed in a shallow silicon region 40 and a reach-through region 18.