Patent ID: 7396732

Claim:
A method for forming a bipolar complementary metal oxide semiconductor device, the method comprising the steps of: patterning a trench having sidewalls in the substrate; depositing an oxide separating layer atop the sidewalls and bottom of the trench; depositing an extra oxide liner atop the oxide separating layer; forming a partially filled-in portion of the trench, wherein the partially filled-in portion comprises a sacrificial material, whereby a portion of the sidewalls is exposed and a portion of the sidewalls is covered by the sacrificial material; depositing spacers on the exposed portion of the sidewalls atop the extra oxide liner, whereby the spacers extend towards the filling material, whereby an opening to the trench is narrowed; removing the sacrificial material though the narrowed opening; sealing the opening by depositing a layer above the spacers, whereby an airgap is formed; and thereafter forming a first field area and a second field area inside the substrate a bipolar transistor in the substrate, wherein the airgap is situated between the first field area and the second field area and comprises part of an active area field isolation module in a bipolar complementary metal oxide semiconductor device thus obtained.