| 摘要 |
PROBLEM TO BE SOLVED: To realize a varactor with good satisfactory modulation characteristics that does not cause deterioration at high frequency waves of a transistor. SOLUTION: An emitter layer 51, an emitter intermediate layer 52, an emitter intermediate layer 53, and an emitter/contact layer 54 each has an n-type impurity density that increases sequentially in this order. In a transistor part 10a, a junction capacity of a p-n junction between a p-type base layer 4 and the emitter layer 51 is limited to a low level, to prevent a decrease in high-frequency characteristics. In a varactor part 11a, an anode electrode 104a is formed in the emitter intermediate layer 53 with high impurity density, and a cathode electrode 105a is formed on the emitter layer 51 with low impurity density to constitute a diode with hyperabrupt junction structure. An alloyed region 6a as an ohmic electrode is formed immediately under the cathode electrode 105a.
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