Semiconductor device, manufacturing thereof and power amplifier module
In a semiconductor device using an emitter top heterojunction bipolar transistor having a planar shape in a ring-like shape, a structure is provided in which a base electrode is present only on an inner side of a ring-like emitter-base junction region. This allows reduction of base/collector junction capacitance per unit emitter area, whereby a semiconductor device having high power adding efficiency and high power gain suitable for a power amplifier can be realized. Further, in a multistage power amplifier including first and second amplifier circuits each having one or more of bipolar transistors, a bipolar transistor in the first amplifier circuit uses an emitter having a planar shape in a rectangular shape, and a bipolar transistor in the second amplifier circuit uses an emitter having a ring-like shape and a base electrode only on the inner side of the emitter.
1. A semiconductor device comprising:
a semiconductor substrate; and
a bipolar transistor formed above the semiconductor substrate and having an emitter/base junction region having a planar shape in a ring-like shape;
wherein the semiconductor substrate is a zinc blende type semiconductor substrate having a (100) (±5 degrees) face, the bipolar transistor is an emitter top type heterojunction bipolar transistor, and a base electrode of the heterojunction bipolar transistor is present on an inner side of the ring-like emitter/base junction region.
2. The semiconductor device according to claim 1 , wherein no side substantially in parallel with [011] direction (±5 degrees) is present on an outer periphery of the emitter/base junction region of the heterojunction bipolar transistor.
3. The semiconductor device according to claim 1 , wherein the planar shape is a polygonal shape.
4. The power amplifier module to claim 2 , wherein a planar shape of the base electrode of the bipolar transistor included by the first amplifier circuit is a quadrangular shape.