Isolation stack for a bipolar transistor and related methods

Abstract

The disclosure provides an isolation stack for a bipolar transistor (BT), and related methods. A structure of the disclosure includes a first isolation layer on a subcollector. A first air gap is between the first isolation layer and a collector of a BT. A second isolation layer is on the first isolation layer and adjacent an intrinsic base of the BT. A third isolation layer is on the second isolation layer, vertically between the second isolation layer and an extrinsic base of the BT. A second air gap is adjacent the third isolation layer and below the extrinsic base.