| 摘要 |
PURPOSE:To reduce the length of a bird beak by forming a projecting impurity diffused region on a semiconductor substrate, forming the region and a silicon nitride film on the step of the periphery through a silicon oxide film, and forming a field oxide film with the nitride film as a mask. CONSTITUTION:Since the growing rates of thermal oxide films are difference on an impurity diffused region 4 and a field region 5 when a silicon oxide film is formed of the thermal oxide film, a projecting impurity diffused region 4 surrounded by a step 6 is formed on a silicon substrate 3. After the oxide film is removed, the silicon oxide film and the silicon nitride film are again formed, they are patterned to allow the impurity diffused layer 4 and a silicon nitride film 1 on the step 6 of the periphery to remain. With the film 1 as a mask it is thermally oxidized to form a field oxide film 2A. In this case, the film 1 is so formed as to cover the step 6 of a boundary between the region 4 and the region 5. Thus, the film 2A in which the length of a bird beak is reduced is provided.
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