| 摘要 |
PURPOSE: A method for forming a gate electrode of a semiconductor device is provided to enable a formation of the gate electrode without reducing the effective length thereof and thereby to prevent lowering of device characteristics. CONSTITUTION: A forming process of a gate electrode begins with a step of thermally growing a gate oxide(200) on a monocrystalline silicon substrate(100). Next, a first and a second polysilicon layers are successively formed on the gate oxide(200) and then patterned to form the gate electrode having lower and upper layers(311,321). The lower layer(311) is preferably thinner than the upper layer(321). Next, ion impurities are implanted into the substrate(100) and the gate electrode, and the ions in the gate electrode are then mostly concentrated in interface between both the layers(311,321). Source and drain regions(101,102) are formed by thermal diffusion, and further, the ions in the interface are diffused toward the lower layer(311). In particular, a bird's beak region(330) occurs at both ends of the interface between the layers(311,321), but does not in interface between the gate oxide(200) and the lower layer(311). Therefore, the effective length(d2) of the gate electrode is not reduced.
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