| 摘要 |
PURPOSE: A method for forming a polysilicon gate is provided to prevent a penetration of boron ions into a gate oxide layer. CONSTITUTION: A semiconductor substrate(61) having a gate oxide layer(62) formed thereon is loaded in a CVD reaction furnace, and the first polysilicon layer is deposited on the substrate(61) while the reaction furnace has a reduced pressure and a reactant gas such as silane is supplied into the reaction furnace. After a deposition of the first polysilicon layer, the reaction furnace is filled with a nitrogen gas so that a pressure in the reaction furnace is increased to an atmospheric pressure. Thus, a strong bond(68) between silicon and nitrogen is produced on the first polysilicon layer. Then, a pressure in the reaction furnace is reduced again, and the silane gas is supplied once more into the reaction furnace to form the second polysilicon layer(70). Next, a polysilicon oxide layer(76) is formed on the second polysilicon layer(70). The silicon and nitrogen bond(68) prevents fluorine ions from spreading out, and further, suppresses a penetration of boron ions by the fluorine ions.
|
