| 摘要 |
PURPOSE: A method for fabricating a semiconductor device is provided to prevent boron ions from penetrating a channel region while a gate depletion of an n-type metal oxide semiconductor(NMOS) transistor is prevented, by forming a structure having a small and irregular grain size. CONSTITUTION: An isolation layer(22) is formed in a field region of a semiconductor substrate(21). A gate insulation layer(23) is formed on the semiconductor substrate. The semiconductor substrate having the gate insulation layer is inserted into a reaction furnace. A deposition gas injecting process, a deposition gas eliminating process and a purification process are repeated to form the first polysilicon layer(24) so that the structure having the small and irregular grain size is formed on the gate insulation layer. The second polysilicon layer(25) is formed on the first polysilicon layer. The first polysilicon layer, the second polysilicon layer and the gate insulation layer are selectively eliminated to form the first and second gate electrodes. Impurity ions of the first conductivity type are implanted into the first gate electrode and the semiconductor substrate adjacent to the first gate electrode. Impurity ions of the second conductivity type are implanted into the second gate electrode and the semiconductor substrate adjacent to the second gate electrode. The impurity ions of the first and second conductivity types are activated.
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