| 摘要 |
In a prior art HEMT, when a high electric field is applied to the gate electrode, two-dimension electrons in the channel layer move to the electron supply layer and the high frequency characteristic is deteriorated. The present invention provides a field effect transistor in which a semiconductor layer having a thickness to spatially separate a two-dimension electron gas from doner ions of an electron supply layer and form two-dimension electron gas in a channel layer by a Coulomb force of the doner ions and having a better high frequency characteristic than that of the electron supply layer is formed between the channel layer and the electron supply layer. In accordance with the present invention, when a high electric field is applied to the two-dimension electron gas and the energy of the electrons increase so that the electrons jump out of the channel layer, the electrons are moved to the semiconductor layer of the predetermined thickness having the good high frequency characteristic, which is adjacent to the channel layer. As a result, even if the high electric field is applied to the channel of the FET, the transport characteristic of the electrons is not deteriorated and the high frequency characteristic of the device is assured.
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