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 circuit element is formed on a substrate made of a compound semiconductor. A bonding pad is disposed on the circuit element so as to at least partially overlap the circuit element. The bonding pad includes a first metal film and a second metal film formed on the first metal film. A metal material of the second metal film has a higher Young's modulus than a metal material of the first metal film.

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 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 compound semiconductor substrate has a first main surface parallel to a first direction and a second direction perpendicular to the first direction, a second main surface located on a side opposite to the first main surface, and a recess. The recess has an opening, a bottom surface facing the opening, and a plurality of side surfaces located between the opening and the bottom surface. The side surfaces include at least one first side surface forming an angle of about ? degrees with the bottom surface in the recess and at least one second side surface forming an angle of about ? degrees with the bottom surface in the recess. The total length of edge lines between the first main surface and the at least one first side surface is larger than that of edge lines between the first main surface and the at least one second side surface.

Abstract: A semiconductor chip includes a single-crystal substrate and a metal electrode on the bottom surface of the substrate. The metal electrode has a region in which a first metal is exposed and a region in which a second metal is exposed, the second metal having a standard electrode potential different from that of the first metal.

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 that includes a bipolar transistor, wherein a third opening, through which a pillar bump and a second wiring line, which is electrically connected to an emitter layer, contact each other, is shifted in a longitudinal direction of the emitter layer away from a position at which the third opening would be directly above the emitter layer. The third opening is arranged, with respect to the emitter layer, such that an end portion of the emitter layer in the longitudinal direction of the emitter layer and the edge of the opening of the third opening are substantially aligned with each other.

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 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 that includes a bipolar transistor, wherein a third opening, through which a pillar bump and a second wiring line, which is electrically connected to an emitter layer, contact each other, is shifted in a longitudinal direction of the emitter layer away from a position at which the third opening would be directly above the emitter layer. The third opening is arranged, with respect to the emitter layer, such that an end portion of the emitter layer in the longitudinal direction of the emitter layer and the edge of the opening of the third opening are substantially aligned with each other.

Abstract: An HBT includes a semiconductor substrate having first and second principal surfaces opposite each other; and a collector layer, a base layer, and an emitter layer stacked in this order on the first principal surface side of the semiconductor substrate. The collector layer includes a first semiconductor layer with metal particles dispersed therein, the metal particles each formed by a plurality of metal atoms bonded with each other.

Abstract: A heterojunction bipolar transistor includes a collector layer, a base layer, an emitter layer, and a semiconductor layer that are laminated in this order, wherein the emitter layer includes a first region having an upper surface on which the semiconductor layer is laminated, and a second region being adjacent to the first region and having an upper surface that is exposed, and the first and second regions of the emitter layer have higher doping concentrations in portions near the upper surfaces than in portions near an interface between the emitter layer and the base layer.

Abstract: An HBT includes a semiconductor substrate having first and second principal surfaces opposite each other; and a collector layer, a base layer, and an emitter layer stacked in this order on the first principal surface side of the semiconductor substrate. The collector layer includes a first semiconductor layer with metal particles dispersed therein, the metal particles each formed by a plurality of metal atoms bonded with each other.

Abstract: A semiconductor device that includes a bipolar transistor, wherein a third opening, through which a pillar bump and a second wiring line, which is electrically connected to an emitter layer, contact each other, is shifted in a longitudinal direction of the emitter layer away from a position at which the third opening would be directly above the emitter layer. The third opening is arranged, with respect to the emitter layer, such that an end portion of the emitter layer in the longitudinal direction of the emitter layer and the edge of the opening of the third opening are substantially aligned with each other.

Abstract: A semiconductor device that includes a bipolar transistor, wherein a third opening, through which a pillar bump and a second wiring line, which is electrically connected to an emitter layer, contact each other, is shifted in a longitudinal direction of the emitter layer away from a position at which the third opening would be directly above the emitter layer. The third opening is arranged, with respect to the emitter layer, such that an end portion of the emitter layer in the longitudinal direction of the emitter layer and the edge of the opening of the third opening are substantially aligned with each other.

Abstract: A semiconductor device that includes a bipolar transistor, wherein a third opening, through which a pillar bump and a second wiring line, which is electrically connected to an emitter layer, contact each other, is shifted in a longitudinal direction of the emitter layer away from a position at which the third opening would be directly above the emitter layer. The third opening is arranged, with respect to the emitter layer, such that an end portion of the emitter layer in the longitudinal direction of the emitter layer and the edge of the opening of the third opening are substantially aligned with each other.

Abstract: A heterojunction bipolar transistor includes a collector layer composed of a semiconductor containing GaAs as a main component; a base layer including a first base layer and a second base layer the first base layer forming a heterojunction with the collector layer and being composed of a semiconductor containing a material as a main component, the material being lattice-mismatched to the main component of the collector layer, the first base layer having a film thickness less than a critical thickness at which a misfit dislocation is introduced, the second base layer being joined to the first base layer and composed of a semiconductor containing a material as a main component, and the material being lattice-matched to the main component of the collector layer; and an emitter layer that forms a heterojunction with the second base layer.

Abstract: In a bipolar transistor, a collector layer includes three semiconductor layers: an n-type GaAs layer (Si concentration: about 5×1015 cm?3, thickness: about 350 nm), a p-type GaAs layer (C concentration: about 4.5×1015 cm?3, thickness: about 100 nm, sheet concentration: 4.5×1010 cm?2), and an n-type GaAs layer Si concentration: about 5×1015 cm?3, thickness: about 500 nm. The sheet concentration of the p-type GaAs layer is set to less than 1×1011 cm?2.

Abstract: P-type second semiconductor layers each interposed between a corresponding pair of n-type first semiconductor layers reduce the apparent doping concentration in the entire collector layer without reducing the doping concentrations in the first semiconductor layers. This improves the linearity of capacitance characteristics and enables sufficient mass productivity to be achieved. Interposing each of the second semiconductor layers between the corresponding pair of the first semiconductor layers reduce the average carrier concentration over the entire collector layer, which allows a wide depletion layer to be formed inside the collector layer and, as a result, reduces base-collector capacitance.