Oxide tub isolation (OTI) is an attractive alternative for bipolar and complementary metal-oxide-semiconductor (BiCMOS) technologies. OTI is a variation of shallow trench isolation in which the trenches reach the buried diffusion layers. This isolation technology affords increased BiCMOS device density and latch-up suppression compared to junction isolation and affords cost advantages over deep trench isolation. Furthermore, this isolation technology affords an increase in bipolar junction transistor device performance due to the reduction of collector-to-substrate capacitance. However, trench-related stress is a formidable challenge in the effective implementation of OTI. Both physical and electrical evidence shows that a Si3N4 trench liner significantly reduces trench-related stress. The Si3N4 trench liner thus affords increased device array yield, as well as improved resistor and metal-oxide-semiconductor field-effect transistor matching.