| 摘要 |
PURPOSE:To increase mobility, by introducing donor impurities in a semiconductor on the side of a gate having a broad forbidden band between a channel and source and drain electrodes, and by not introducing the impurities into the channel part directly beneath the gate electrode. CONSTITUTION:A nondoped first semiconductor layer 24 and a second semiconductor layer 25 are formed by heterojunctions. The forbidden band of the first semiconductor layer 24 is made smaller than that of the second semiconductor layer 25. A high concentration impurity region 28 is provided in the second semiconductor layer 25. A source electrode region 29 and a drain electrode region 30 are formed by an ordinary alloy method. A gate electrode 26 is formed in order to control carriers yielded in the vicinity of a heterojunction. The channel region of the first semiconductor layer 24 is made to be a low impurity concentration region, and an impurity layer 23 is provided in the first semiconductor layer 24. Thus, the FET, in which mobility and mutual conductance are made large, can be formed.
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