Process for simultaneously fabricating isolation structures for bipolar and CMOS circuits

摘要

An isolation structure for bipolar and CMOS circuits formed during the same processing steps to optimize the integration of bipolar and CMOS circuits. A deep trench (46) is formed in a semiconductor circuit for providing deep isolation for bipolar circuits. A shallow recess (56) is then formed simultaneous with a stepped sidewall structure of the deep trench. The recess (56) and the trench (46) are covered by an insulating oxide (60). and thereafter filled with an undoped polysilicon (62) to form the different isolating structures for the different types of circuits.