Abstract: A method for forming a trench isolation region within a trench within a silicon substrate. There is first provided a silicon substrate having a trench formed therein. There is then formed over the silicon substrate and filling the trench a silicon oxide trench fill layer. There is then thermally oxidized the silicon substrate and the silicon oxide trench fill layer within a thermal oxidation atmosphere to form a densified silicon oxide trench fill layer upon a silicon oxide trench liner layer within an oxidized trench within an oxidized silicon substrate, where the silicon oxide trench liner layer is formed from oxidation of the silicon substrate when forming the oxidized silicon substrate.