By forming a non-oxidizable liner in an isolation trench and selectively modifying the liner within the isolation trench, the stress characteristics of the isolation trench may be adjusted. In one embodiment, a high compressive stress may be obtained by treating the liner with an ion bombardment and subsequently exposing the device to an oxidizing ambient at elevated temperatures, thereby incorporating silicon dioxide into the non-oxidizable material. Hence, an increased compressive stress may be generated within the non-oxidizable layer.