| 摘要 |
PURPOSE: A method of forming a device isolation layer is provided to reduce an edge dent or a recess in a trench isolation and to improve uniformity of a LOCOS isolation. CONSTITUTION: In a formation of a device isolation, a trench(5) is formed in a semiconductor substrate(2) by using an etch mask such as silicon nitride layer. The trench(5) is then filled with an oxide layer as a trench isolation(6). Next, the trench isolation(6) is chemically and mechanically polished and the etch mask is removed by a strip process. Subsequently, a series of processes such as a photomasking, an ion implantation, an ashing, and a strip are repeatedly performed before forming of a gate stack. In particular, a high dose ion implantation step is carried out for the last time for a control of cell threshold voltage. Therefore, a dent(8) in an edge of the trench isolation(6) is reduced, and furthermore, a surface recess of the trench isolation(6) is reduced.
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