Methods of forming a dielectric layer where the tensile stress of the layer is increased by a plasma treatment at an elevated position are described. In one embodiment, oxide and nitride layers are deposited on a substrate and patterned to form an opening. A trench is etched into the substrate. The substrate is transferred into a chamber suitable for dielectric deposition. A dielectric layer is deposited over the substrate, filling the trench and covering mesa regions adjacent to the trench. The substrate is raised to an elevated position above the substrate support and exposed to a plasma which increases the tensile stress of the substrate. The substrate is removed from the dielectric deposition chamber, and portions of the dielectric layer are removed so that the dielectric layer is even with the topmost portion of the nitride layer. The nitride and pad oxide layers are removed to form the STI structure.