MOS field-effect transistor comprising layered structure including Si layer and SiGe layer OR SiGeC layer as channel regions

摘要

The MOS field-effect transistor aims to enhance the electron mobility and the hole mobility in the channel portion by employing the strained-Si/SiGe (or Si/SiGeC) structure. Crystallinity of such a heterostructure is maintained in a preferable state, shortening of the effective channel length is prevented, diffusion of Ge is prevented and the resistance of the source layer and the drain layer is reduced. The channel region has a layered structure formed by stacking the Si layer and, the SiGe or SiGeC layer in order from the surface. The source layer and the drain layer formed of SiGe or SiGeC including high concentration impurity atoms providing a desired conduction type, are in contact with both end surfaces of the channel region. The surfaces of the source layer and the drain layer have a shape rising upwardly from the bottom portion of the gate electrode.