| abstract |
The quality of an ultra thin gate oxide film, particularly at the edges of a shallow trench isolation structure, is improved employing a double sacrificial oxide technique. After trench filling and planarization, the pad oxide layer thickness is increased during trench fill densification in an oxidizing atmosphere. The pad oxide is then removed exposing the substrate surface and trench edges. A second sacrificial oxide is formed consuming part of the substrate surface. The second sacrificial oxide is then removed along with defects in the substrate surface prior to gate oxide and gate electrode formation. |