Abstract: The object of the present invention is to provide a heterojunction bipolar transistor with high breakdown tolerance which can be manufactured at a high reproducibility and a high yield, the heterojunction bipolar transistor includes: a sub-collector layer; a collector layer formed on the sub-collector layer; a base layer formed on the collector layer; and an emitter layer, which is formed on the base layer and is made of a semiconductor that has a larger bandgap than a semiconductor of the base layer, in which the collector layer includes: a first collector layer formed on the sub-collector layer; a second collector layer formed on the first collector layer; and a third collector layer formed between the second collector layer and the base layer, a semiconductor of the first collector layer differs from semiconductors of the third collector layer and the second collector layer, and an impurity concentration of the second collector layer is lower than an impurity concentration of the sub-collector layer and hi

Abstract: A semiconductor device has an interconnect layer for providing an electric connection between a base electrode and a base terminal provided on the region of a semi-insulating substrate on which a transistor is not formed. A resistor layer composed of a material different from respective materials composing the base electrode and the interconnect layer is formed on the base electrode and the base electrode and the interconnect layer are connected to each other via the resistor layer.

Abstract: On a high-concentration n-type first sub-collector layer, a high-concentration n-type second sub-collector layer made of a material having a small bandgap, an i-type or low-concentration n-type collector layer, a high-concentration p-type base layer, an n-type emitter layer made of a material having a large bandgap, a high-concentration n-type emitter cap layer, a high-concentration n-type emitter contact layer made of a material having a small bandgap are sequentially stacked. From the emitter contact layer, an interconnection also serving as an emitter electrode is extended. From the emitter layer or the base layer, an interconnection also serving as a base electrode is extended. From the second sub-collector layer, an interconnection also serving as a collector electrode is extended.

Abstract: The following layers are successively formed on a heavily-doped n-type first subcollector layer: a heavily-doped n-type second subcollector layer made of a material having a small band gap; an i-type or a lightly-doped n-type collector layer; a heavily-doped p-type base layer; an n-type emitter layer made of a material having a large band gap; a heavily-doped n-type emitter cap layer; and a heavily-doped n-type emitter contact layer made of a material having a small band gap. Alloying reaction layers are formed under an emitter electrode, a base electrode and a collector electrode.

Abstract: The following layers are successively formed on a heavily-doped n-type first subcollector layer: a heavily-doped n-type second subcollector layer made of a material having a small band gap; an i-type or a lightly-doped n-type collector layer; a heavily-doped p-type base layer; an n-type emitter layer made of a material having a large band gap; a heavily-doped n-type emitter cap layer; and a heavily-doped n-type emitter contact layer made of a material having a small band gap. Alloying reaction layers are formed under an emitter electrode, a base electrode and a collector electrode.

Abstract: The push button switch covering assembly of the invention comprises a push button switch covering member made from a transparent rubbery material and a clicking member with a clicking diaphragm below the covering member which imparts the operator's finger tip with a sharp feeling of clicking when the key top of the covering member is depressed.