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 bipolar transistor includes an upper sub-collector layer, a collector layer, a base layer, an emitter layer, and a collector electrode. The collector layer is disposed on the upper sub-collector layer. The base layer is disposed on the collector layer. An emitter layer is disposed on the base layer. The collector electrode is disposed directly on a sidewall of the upper sub-collector layer.

In an aspect, a heterojunction bipolar transistor (HBT) includes a sub-collector disposed on a collector. The collector has a collector contact disposed on the sub-collector and located on a first side of the heterojunction bipolar transistor. The HBT includes an emitter disposed on an emitter cap. The emitter has an emitter contact disposed on the emitter cap and located on a second side of the heterojunction bipolar transistor. The HBT includes a base having a base contact located on the second side of the heterojunction bipolar transistor.

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.

The present disclosure provides an HBT that includes (i) a semiconductor support layer; at least four wall structures side-by-side on the support layer; (iii) a semiconductor collector-material ridge structure disposed on the support layer between two adjacent wall structures of the at least four wall structures; (iv) a semiconductor base-material layer, wherein a first part of the base-material layer is disposed on a first region of the ridge structure and a second part of the base-material layer is disposed across the wall structures, wherein the base-material layer is supported by the wall structures; (v) a semiconductor emitter-material layer disposed on the first part of the base-material layer; (vi) a base contact layer disposed on the second part of the base-material layer; an emitter contact layer disposed on the emitter-material layer; and (viii) a collector contact layer disposed on a second region of the ridge structure.

A first collector layer is composed of n-type InP (n-InP) doped with Si at a low concentration. A second collector layer is composed of non-doped InGaAs. A base layer is composed of p-type GaAsSb (p.sup.+-GaAsSb) doped with C at a high concentration. An emitter layer is composed of a compound semiconductor different from that of the base layer, and has an area smaller than the base layer in a plan view. An emitter layer can be composed of, for example, n-type InP (n-InP) doped with Si at a low concentration.

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.

A semiconductor device includes a substrate having an upper surface on which are arranged first transistors each including a mesa structure formed of a semiconductor. A first bump having a shape elongated in one direction in plan view and connected to the first transistors is arranged at a position overlapping the first transistors in plan view. A second bump has a space with respect to the first bump in a direction orthogonal to a longitudinal direction of the first bump. A first metal pattern is arranged between the first and second bumps in plan view. When the upper surface of the substrate is taken as a height reference, a center of the first metal pattern in a thickness direction has a height higher than an upper surface of the mesa structure included in each of the first transistors and lower than a lower surface of the first bump.

Methods of manufacturing heterojunction bipolar transistors are described herein. An exemplary method can include providing an emitter/base stack comprising a substrate, a base over the substrate, and/or an emitter over the base. The exemplary method further can include forming a collector. The exemplary method also can include wafer bonding the base to the collector. Other embodiments are also disclosed herein.

A bipolar junction transistor (LBJT) device that includes a base region of a first III-V semiconductor material having A first band gap; and emitter and collector regions present on opposing sides of the base region, wherein the emitter and collector regions are comprised of a second III-V semiconductor material having a wider band gap than the first III-V semiconductor material. A dielectric region is present underlying the base region, emitter region and the collect region. The dielectric region has an inverted apex geometry. The sidewalls of dielectric region that extend to the apex of the inverted apex geometry are present on facets of a supporting substrate III-V semiconductor material having a {110} crystalline orientation.