| 摘要 |
PURPOSE: A method for forming an isolation layer of a semiconductor device is provided to prevent a moat phenomenon causing a ditch around the isolation layer in a shallow trench isolation process and thereby to suppress the degradation of a threshold voltage. CONSTITUTION: A pad oxide layer and a pad nitride layer are formed on a semiconductor substrate, and then an isolation mask is formed on the pad nitride layer. By using the mask, the pad nitride layer, the pad oxide layer and the substrate are sequentially etched to form a trench(S11). A sidewall of the trench is then subjected to a sacrificial oxidation and a sidewall oxidation(S12). Next, on a resultant structure, a liner oxide layer is formed to prevent later the moat phenomenon of a field oxide layer(S13), and then condensed(14). Next, a high density plasma oxide layer is formed as the field oxide layer on a resultant structure(S15), and then chemically mechanically polished to define the field oxide layer filled in the trench(S16). Thereafter, the pad nitride layer is removed through a cleaning process using H3PO4 only without using conventional BOE(S17).
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