A bipolar transistor includes a collector layer, a base layer on the collector layer, and a first elongated emitter mesa on the base layer having a long side and a short side, wherein the long side is parallel with a first direction, and n separate first emitter-contact structures disposed along the first direction on the first elongated emitter mesa, where n is an integer greater than one.

A semiconductor element includes a semiconductor substrate; a collector layer on the semiconductor substrate; a base layer on the collector layer; an emitter layer on the base layer; emitter wiring electrically coupled to the emitter layer; a top metal layer on the emitter wiring; a first protective film covering the emitter wiring and the top metal layer, the first protective film having a first opening that overlaps at least the collector layer; and a bump including an under-bump metal layer electrically coupled to the emitter wiring via the first opening, the under-bump metal layer being larger than the first opening in plan-view area. The first protective film has an inner edge around the first opening, and the inner edge is on the top metal layer.

Structures for a heterojunction bipolar transistor and methods of forming a structure for a heterojunction bipolar transistor. A first portion of a first semiconductor layer defines an emitter, a first portion of a second semiconductor layer defines a collector, and a base includes respective second portions of the first and second semiconductor layers that are laterally positioned between the first portion of the first semiconductor layer and the first portion of the second semiconductor layer. The first portion of the first semiconductor layer has a first thickness, and the first portion of the second semiconductor layer has a second thickness that is greater than the first thickness. The first portion and the second portion of the first semiconductor layer adjoin at a first junction having the first thickness. The first portion and the second portion of the second semiconductor layer adjoin at a second junction having the second thickness.

Structures for a heterojunction bipolar transistor and methods of forming a structure for a heterojunction bipolar transistor. A first portion of a first semiconductor layer defines an emitter, a first portion of a second semiconductor layer defines a collector, and a base includes respective second portions of the first and second semiconductor layers that are laterally positioned between the first portion of the first semiconductor layer and the first portion of the second semiconductor layer. The first portion of the first semiconductor layer has a first thickness, and the first portion of the second semiconductor layer has a second thickness that is greater than the first thickness. The first portion and the second portion of the first semiconductor layer adjoin at a first junction having the first thickness. The first portion and the second portion of the second semiconductor layer adjoin at a second junction having the second thickness.

One illustrative method of forming heterojunction bipolar devices includes, among other things, forming a first gate structure above an active semiconductor layer, forming a second gate structure adjacent a first side of the first gate structure, forming a third gate structure adjacent a second side of the first gate structure, forming an emitter of a bipolar transistor in the active semiconductor layer between the first gate structure and the second gate structure, forming a collector of the bipolar transistor in the active semiconductor layer between the first gate structure and the third gate structure, and forming a first base contact contacting the active region adjacent an end of the first gate structure, wherein a portion of the active semiconductor layer positioned under the first gate structure defines a base of the bipolar transistor.

Provided is a high ruggedness HBT, including a first emitter cap layer and a second emitter cap layer formed between an emitter layer and an ohmic contact layer, or only an emitter cap layer is formed between them. When the first and second emitter cap layers are provided, bandgaps of the first or second emitter cap layer are changed, and the ruggedness of the HBT is improved. When an emitter cap layer is provided, an electron affinity of at least a portion of the emitter cap layer is less than or approximately equal to an electron affinity of the emitter layer, and the ruggedness of the HBT is improved.

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.

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.

A method of making a bipolar transistor includes forming a stack of a first, second, third and fourth insulating layers on a substrate. An opening is formed in the stack to reach the substrate. An epitaxial process forms the collector of the transistor on the substrate and selectively etches an annular opening in the third layer. The intrinsic part of the base is then formed by epitaxy on the collector, with the intrinsic part being separated from the third layer by the annular opening. The junction between the collector and the intrinsic part of the base is surrounded by the second layer. The emitter is formed on the intrinsic part and the third layer is removed. A selective deposition of a semiconductor layer on the second layer and in direct contact with the intrinsic part forms the extrinsic part of the base.

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.