| 摘要 |
PURPOSE:To improve the reliability of nonvolatile semiconductor memory device of double gate structure by forming a double gate structure and source and drain region, then forming a thin oxidized silicon film, protecting surface, to which B and P are added, growing the stabilized film, and flattening by high temperature heat treating the surface of the same film. CONSTITUTION:After the first gate oxidized film 2, the first gate polycrystalline silicon film 3, the second gate oxidized film 4 and the second gate polycrystalline silicon film 5 are formed by self-aligning on a silicon substrate 1, P, As, B and the like is implanted by thermal diffusion method or ion implanting method in high density on the substrate 1, thereby forming source and drain region 6. Then, the exposed parts of the first and second gate polycrystalline silicon films 3, 5 and the third thin oxidized silicon film 8 are formed on the region 6 of the substrate by heat treating in the H2/O2. Further, a PSG film 9 which contains 2mol% of P, 1mol% of B are, for example, is grown by a gas phase growing method thereon, heat treated in H2/O2 atmosphere, thereby flattening the surface of the film 9. |
