Patent ID: 7846789

Claim:
A method of manufacturing a semiconductor device, comprising: forming a bipolar complementary metal oxide semiconductor (BiCMOS) device including: forming a semiconductor layer on a semiconductor substrate, wherein said semiconductor layer and said substrate include a same first dopant type, and a concentration of said first dopant is greater in said substrate than in said semiconductor layer; forming a metal oxide semiconductor (MOS) transistor on or in said semiconductor layer; forming a bipolar transistor on or in said semiconductor layer; and forming an insulating trench located between said MOS transistor and said bipolar transistor, wherein said insulating trench is formed through said semiconductor layer and into said substrate and at least one top corner of said insulating trench is formed as a rounded corner in a lateral plane of said substrate; forming insulating layers on said substrate and covering said BiCMOS device; and forming interconnects through one or more of said insulating layers to electrically connect said MOS transistor and bipolar transistor to each other, or to other active or passive components of said semiconductor device; wherein said insulating trench is formed with four linear segments that are coupled together by connecting corners to form a ring that surrounds at least one of said MOS transistor device or said bipolar transistor device; and wherein at least one of said connecting corners has said at least one top corner.