| 摘要 |
PROBLEM TO BE SOLVED: To provide a field effect semiconductor device for power amplification which has lower channel conductance as well as a higher cut-off frequency and higher load efficiency than an Si-system field effect transistor. SOLUTION: A semiconductor layer structure comprises a first conductivity type Si substrate and a first conductivity type high impurity concentration first SiGe layer, a first conductivity type low impurity concentration second SiGe layer, and a low impurity concentration Si layer which are layered on the first conductivity type Si substrate in this order, a channel is formed in a part of the Si layer, and a source electrode is formed so as to pierce through the low impurity concentration second SiGe layer and brought into electrical contact with the high impurity concentration first SiGe layer as well as the substrate. With such a constitution, a field effect semiconductor device for power amplification which can operate with a high speed and high efficiency can be realized.
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