Method for making bipolar transistor having an enhanced trench isolation

Abstract

Disclosed is a fabrication of a bipolar transistor using an enhanced trench isolation so as to improve integration and performance thereof, comprising the steps of sequentially etching back portions corresponding to a trench using a trench forming mask to a predetermined depth of the buried collector to form the trench; filling an isolation insulating layer into the trench; polishing the isolation insulating layer up to a surface of the silicon oxide layer; sequentially forming a second insulating layer on the isolating insulating layer and the silicon oxide layer; removing the first polysilicon layer and the first insulating layer formed on an inactive region other than an active region defined by the trench; thermal-oxidizing the collector layer formed on the inactive region to form a thermal oxide layer; removing the second insulating layer and sequentially forming a third polysilicon, a third insulating layer and a second nitride layer; etching back layers formed on a portion of the first insulating layer to form an opening in the active region; forming a first side wall on both edges of the opening and removing the first insulating layer; forming an intrinsic base at a region where the first insulating layer is removed to electrically connect the intrinsic base with an extrinsic base in self-alignment; forming a second side wall on both sides of the first side wall; and forming an emitter layer on the intrinsic base.