| 摘要 |
A field effect transistor comprising first and second electrodes, semiconductor layers connected to these electrodes to form a carrier channel between them and a control electrode is provided. Said semiconductor layers consisting essentially of: (a) a first semiconductor layer of a first semiconductor material having a low density of state of carrier formed on a substrate, (b) a second semiconductor layer of a second semiconductor material containing an impurity element and having a high density of state of carrier formed on the first semiconductor layer, and (c) a third semiconductor layer of a third semiconductor material having a low density of state of carrier formed on the second semiconductor layer, wherein the impurity element contained in the second semiconductor layer is of n-type when the carrier is an electron or of p-type when the carrier is a hole. By such combination as above of layers of low carrier density of state but high carrier mobility layers and a layer of low carrier mobility but high carrier density of state, higher concentration doping has been made possible. This is effective to realize a high performance FET suitable for larger scale integration.
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