Abstract: A semiconductor device includes a heterojunction bipolar transistor and a bump. The heterojunction bipolar transistor (HBT) includes a plurality of unit transistors. The bump is electrically connected to emitters of the plurality of unit transistors through respective overlying conductor filled via openings that overlap in a plan view with a width portion of the bump. The semiconductor device reduces heat resistance in an HBT cell by satisfying two conditions, the first of which is related to specific sizing and positioning of a width portion of the overlying via opening relative to the width portion of the bump, and the second of which is related to positioning the base electrode entirely within a specific region of the width portion of the overlapping overlying via opening.

Abstract: A power amplifier module includes a first amplifier circuit that amplifies a radio frequency signal with a first gain corresponding to a first control signal to generate a first amplified signal; a second amplifier circuit that amplifies the first amplified signal with a second gain corresponding to a second control signal to generate a second amplified signal; and a control unit that generates the first control signal and the second control signal. The second control signal is a control signal for increasing a power-supply voltage for the second amplifier circuit as a peak-to-average power ratio of the radio frequency signal increases. The first control signal is a control signal for controlling the first gain of the first amplifier circuit so that a variation in the second gain involved in a variation in the power-supply voltage for the second amplifier circuit is compensated for.

Abstract: A heterojunction bipolar transistor includes a collector layer, a base layer, and an emitter layer that are stacked on a substrate. The collector layer includes a graded semiconductor layer in which an electron affinity increases from a side closer to the base layer toward a side farther from the base layer. An electron affinity of the base layer at an interface closer to the collector layer is equal to an electron affinity of the graded semiconductor layer at an interface closer to the base layer.

Abstract: A collector layer, a base layer, an emitter layer, and an emitter mesa layer are placed above a substrate in this order. A base electrode and an emitter electrode are further placed above the substrate. The emitter mesa layer has a long shape in a first direction in plan view. The base electrode includes a base electrode pad portion spaced from the emitter mesa layer in the first direction. An emitter wiring line and a base wiring line are placed on the emitter electrode and the base electrode, respectively. The emitter wiring line is connected to the emitter electrode via an emitter contact hole. In the first direction, the spacing between the edges of the emitter mesa layer and the emitter contact hole on the side of the base wiring line is smaller than that between the emitter mesa layer and the base wiring line.

Abstract: A bipolar transistor has a subcollector layer and a stack of collector, base, and emitter layers on the subcollector layer. On the subcollector layer are collector electrodes. On the base layer are base electrodes. The collector layer includes multiple doped layers with graded impurity concentrations, higher on the subcollector layer side and lower on the base layer side. Of these doped layers, the one having the highest impurity concentration is in contact with the subcollector layer and has a sheet resistance less than or equal to about nine times that of the subcollector layer.

Abstract: A semiconductor device includes two cell rows, each of which is formed of a plurality of transistor cells aligned in parallel to each other. Each of the plurality of transistor cells includes a collector region, a base region, and an emitter region that are disposed above a substrate. A plurality of collector extended wiring lines are each connected to the collector region of a corresponding one of the plurality of transistor cells and are extended in a direction intersecting an alignment direction of the plurality of transistor cells. A collector integrated wiring line connects the plurality of collector extended wiring lines to each other. A collector intermediate integrated wiring line that is disposed between the two cell rows in plan view connects the plurality of collector extended wring lines extended from the plurality of transistor cells that belong to one of the two cell rows to each other.

Abstract: A cavity elongated in one direction is formed in a protective film covering the conductive pattern of the topmost conductive layer of a multilayer wiring substrate. The cavity exposes part of the conductive pattern. A first via-conductor extends downward from the conductive pattern of the topmost conductive layer at least until that of a second conductive layer. Second via-conductors extend downward from the conductive pattern of the second or third conductive layer at least until that of a conductive layer one below. As viewed from above, the first via-conductor and the cavity partially overlap each other. At least two second via-conductors are disposed to sandwich the cavity therebetween. The difference between the smallest gap between the cavity and the second via-conductor at one side and that between the cavity and the second via-conductor at the other side is smaller than the smallest gap between the cavity and the second via-conductors.

Abstract: A heterojunction bipolar transistor includes a collector layer, a base layer, and an emitter layer that are stacked on a substrate. The collector layer includes a graded semiconductor layer in which an electron affinity increases from a side closer to the base layer toward a side farther from the base layer. An electron affinity of the base layer at an interface closer to the collector layer is equal to an electron affinity of the graded semiconductor layer at an interface closer to the base layer.

Abstract: A semiconductor device includes a collector layer, a base layer, and an emitter layer that are disposed above a substrate. An emitter mesa layer is disposed on a partial region of the emitter layer. In a plan view, the base electrode is disposed in or on a region which does not overlap the emitter mesa layer. The base electrode allows base current to flow to the base layer. In the plan view, a first edge forming part of edges of the emitter mesa layer extends in a first direction, and a second edge forming part of edges of the base electrode faces the first edge. A gap between the first edge and the second edge in a terminal portion located in an end portion of the emitter mesa layer in the first direction is wider than a gap in an intermediate portion of the emitter mesa layer.

Abstract: A semiconductor device includes a plurality of unit transistors that are arranged on a surface of a substrate in a first direction. Input capacitive elements are arranged so as to correspond to the unit transistors. An emitter common wiring line is connected to emitter layers of the unit transistors. A via-hole extending from the emitter common wiring line to a back surface of the substrate is disposed at a position overlapping the emitter common wiring line. A collector common wiring line is connected to collector layers of the unit transistors. The input capacitive elements, the emitter common wiring line, the unit transistors, and the collector common wiring line are arranged in this order in a second direction. Base wiring lines that connect the input capacitive elements to base layers of the corresponding unit transistors intersect the emitter common wiring line without physical contact.

Abstract: A bipolar transistor has a subcollector layer and a stack of collector, base, and emitter layers on the subcollector layer. On the subcollector layer are collector electrodes. On the base layer are base electrodes. The collector layer includes multiple doped layers with graded impurity concentrations, higher on the subcollector layer side and lower on the base layer side. Of these doped layers, the one having the highest impurity concentration is in contact with the subcollector layer and has a sheet resistance less than or equal to about nine times that of the subcollector layer.

Abstract: A bipolar transistor includes a collector layer, a base layer, and an emitter layer that are formed in this order on a compound semiconductor substrate. The emitter layer is disposed inside an edge of the base layer in plan view. A base electrode is disposed on partial regions of the emitter layer and the base layer so as to extend from an inside of the emitter layer to an outside of the base layer in plan view. An insulating film is disposed between the base electrode and a portion of the base layer, with the portion not overlapping the emitter layer. An alloy layer extends from the base electrode through the emitter layer in a thickness direction and reaches the base layer. The alloy layer contains at least one element constituting the base electrode and elements constituting the emitter layer and the base layer.

Abstract: A collector layer of an HBT includes a high-concentration collector layer and a low-concentration collector layer thereon. The low-concentration collector layer includes a graded collector layer in which the energy band gap varies to narrow with increasing distance from the base layer. The electron affinity of the semiconductor material for the base layer is greater than that of the semiconductor material for the graded collector layer at the point of the largest energy band gap by about 0.15 eV or less. The electron velocity in the graded collector layer peaks at a certain electric field strength. In the graded collector layer, the strength of the quasi-electric field, an electric field that acts on electrons as a result of the varying energy band gap, is between about 0.3 times and about 1.8 times the peak electric field strength, the electric field strength at which the electron velocity peaks.

Abstract: A bipolar transistor includes a collector layer, a base layer, and an emitter layer that are formed in this order on a compound semiconductor substrate. The emitter layer is disposed inside an edge of the base layer in plan view. A base electrode is disposed on partial regions of the emitter layer and the base layer so as to extend from an inside of the emitter layer to an outside of the base layer in plan view. An insulating film is disposed between the base electrode and a portion of the base layer, with the portion not overlapping the emitter layer. An alloy layer extends from the base electrode through the emitter layer in a thickness direction and reaches the base layer. The alloy layer contains at least one element constituting the base electrode and elements constituting the emitter layer and the base layer.

Abstract: A collector layer of an HBT includes a high-concentration collector layer and a low-concentration collector layer thereon. The low-concentration collector layer includes a graded collector layer in which the energy band gap varies to narrow with increasing distance from the base layer. The electron affinity of the semiconductor material for the base layer is greater than that of the semiconductor material for the graded collector layer at the point of the largest energy band gap by about 0.15 eV or less. The electron velocity in the graded collector layer peaks at a certain electric field strength. In the graded collector layer, the strength of the quasi-electric field, an electric field that acts on electrons as a result of the varying energy band gap, is between about 0.3 times and about 1.8 times the peak electric field strength, the electric field strength at which the electron velocity peaks.

Abstract: A semiconductor device includes a plurality of unit transistors that are arranged on a surface of a substrate in a first direction. Input capacitive elements are arranged so as to correspond to the unit transistors. An emitter common wiring line is connected to emitter layers of the unit transistors. A via-hole extending from the emitter common wiring line to a back surface of the substrate is disposed at a position overlapping the emitter common wiring line. A collector common wiring line is connected to collector layers of the unit transistors. The input capacitive elements, the emitter common wiring line, the unit transistors, and the collector common wiring line are arranged in this order in a second direction. Base wiring lines that connect the input capacitive elements to base layers of the corresponding unit transistors intersect the emitter common wiring line without physical contact.

Abstract: A bipolar transistor has a subcollector layer and a stack of collector, base, and emitter layers on the subcollector layer. On the subcollector layer are collector electrodes. On the base layer are base electrodes. The collector layer includes multiple doped layers with graded impurity concentrations, higher on the subcollector layer side and lower on the base layer side. Of these doped layers, the one having the highest impurity concentration is in contact with the subcollector layer and has a sheet resistance less than or equal to about nine times that of the subcollector layer.

Abstract: A power amplifier module includes a first substrate and a second substrate, at least part of the second substrate being disposed in a region overlapping the first substrate. The second substrate includes a first amplifier circuit and a second amplifier circuit. The first substrate includes a first transformer including a primary winding having a first end and a second end and a secondary winding having a first end and a second end; a second transformer including a primary winding having a first end and a second end and a secondary winding having a first end and a second end; and multiple first conductors disposed in a row between the first transformer and the second transformer, each of the multiple first conductors extending from the wiring layer on a first main surface to the wiring layer on a second main surface of the substrate.

Abstract: A semiconductor device has a semiconductor substrate, and multiple first bipolar transistors on the first primary surface side of the semiconductor substrate. The first bipolar transistors have a first height between an emitter layer and an emitter electrode in the direction perpendicular to the first primary surface. The semiconductor device further has at least one second bipolar transistor on the first primary surface side of the semiconductor substrate. The second bipolar transistor have a second height, greater than the first height, between an emitter layer and an emitter electrode in the direction perpendicular to the first primary surface. Also, the semiconductor has a first bump stretching over the multiple first bipolar transistors and the at least one second bipolar transistor.

Abstract: A bipolar transistor has a subcollector layer and a stack of collector, base, and emitter layers on the subcollector layer. On the subcollector layer are collector electrodes. On the base layer are base electrodes. The collector layer includes multiple doped layers with graded impurity concentrations, higher on the subcollector layer side and lower on the base layer side. Of these doped layers, the one having the highest impurity concentration is in contact with the subcollector layer and has a sheet resistance less than or equal to about nine times that of the subcollector layer.