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.

A first wiring is disposed above operating regions of plural unit transistors formed on a substrate. A second wiring is disposed above the substrate. An insulating film is disposed on the first and second wirings. First and second cavities are formed in the insulating film. As viewed from above, the first and second cavities entirely overlap with the first and second wirings, respectively. A first bump is disposed on the insulating film and is electrically connected to the first wiring via the first cavity. A second bump is disposed on the insulating film and is electrically connected to the second wiring via the second cavity. As viewed from above, at least one of the plural operating regions is disposed within the first bump and is at least partially disposed outside the first cavity. The planar configuration of the first cavity and that of the second cavity are substantially identical.

A method of manufacturing a semiconductor device is provided. The method includes: providing a substrate including a first semiconductive region of a first conductive type and gate structures over the first semiconductive region, wherein a gap between the gate structures exposes a portion of the first semiconductive region; and forming a second semiconductive region of a second conductive type in the gap starting from the exposed portion of the first semiconductive region. The forming of the second semiconductive region includes: growing, in a chamber, an epitaxial silicon-rich layer having a first sidewall adjacent to the gate structures and a first central portion; and, in the chamber, shaping the epitaxial silicon-rich layer to form a second sidewall adjacent to the gate structures and a second central portion, wherein a first height difference between the first sidewall and the first central portion is greater than a second height difference between the second sidewall and the second central portion.

Structures for a cascode integrated circuit and methods of forming such structures. A field-effect transistor of the structure includes a gate electrode finger, a first source/drain region, and a second source/drain region. A bipolar junction transistor of the structure includes a first terminal, a base layer with an intrinsic base portion arranged on the first terminal, and a second terminal that includes one or more fingers arranged on the intrinsic base portion of the base layer. The intrinsic base portion of the base layer is arranged in a vertical direction between the first terminal and the second terminal. The first source/drain region is coupled with the first terminal, and the first source/drain region at least partially surrounds the bipolar junction transistor.

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.

A first wiring is disposed above operating regions of plural unit transistors formed on a substrate. A second wiring is disposed above the substrate. An insulating film is disposed on the first and second wirings. First and second cavities are formed in the insulating film. As viewed from above, the first and second cavities entirely overlap with the first and second wirings, respectively. A first bump is disposed on the insulating film and is electrically connected to the first wiring via the first cavity. A second bump is disposed on the insulating film and is electrically connected to the second wiring via the second cavity. As viewed from above, at least one of the plural operating regions is disposed within the first bump and is at least partially disposed outside the first cavity. The planar configuration of the first cavity and that of the second cavity are substantially identical.

In certain aspects, a heterojunction bipolar transistor (HBT) comprises a collector mesa, a base mesa on the collector mesa, and an emitter mesa on the base mesa. The base mesa has a tapered sidewall tapering from a wide bottom to a narrow top. The HBT further comprises a collector contact on a portion of the collector mesa and extending to a portion of the tapered sidewall of the base mesa.

A method of manufacturing a semiconductor device includes: providing a substrate including a first semiconductive region of a first conductive type and gate structures over the first semiconductive region, where a gap between the gate structures exposes a portion of the first semiconductive region; and forming a second semiconductive region of a second conductive type in the gap starting from the exposed portion of the first semiconductive region. The forming of the second semiconductive region includes: growing, in a chamber, an epitaxial silicon-rich layer with a first growth rate around a sidewall adjacent to the gate structures that is greater than a second growth rate at a central portion; and, in the chamber, partially removing the epitaxial silicon-rich layer with an etchant with a first etching rate around the sidewall adjacent to the gate structures that is greater than a second etching rate at the central portion.

A collector layer, a base layer, and an emitter layer that are disposed on a substrate form a bipolar transistor. An emitter electrode is in ohmic contact with the emitter layer. The emitter layer has a shape that is long in one direction in plan view. A difference in dimension with respect to a longitudinal direction of the emitter layer between the emitter layer and an ohmic contact interface at which the emitter layer and the emitter electrode are in ohmic contact with each other is larger than a difference in dimension with respect to a width direction of the emitter layer between the emitter layer and the ohmic contact interface.

In certain aspects, a heterojunction bipolar transistor (HBT) comprises a collector mesa, a base mesa on the collector mesa, and an emitter mesa on the base mesa. The base mesa has a tapered sidewall tapering from a wide bottom to a narrow top. The HBT further comprises a collector contact on a portion of the collector mesa and extending to a portion of the tapered sidewall of the base mesa.