Kabushiki Kaisha Toshiba

Kunio Tsuda

Akira Yoshioka

Toru Sugiyama

Yasunobu Saito

Tetsuya Ohno

Kouhei Morizuka

Riichi Katoh

A semiconductor device according to one embodiment includes an n-type first GaN-based semiconductor layer, a p-type second GaN-based semiconductor layer on the first GaN-based semiconductor layer. The second GaN-based semiconductor layer includes a low impurity concentration region and a high impurity concentration region. An n-type third GaN-based semiconductor layer is provided on the second GaN-based semiconductor layer. The device includes a gate electrode being located adjacent to the third GaN-based semiconductor layer, the low impurity concentration region, and the first GaN-based semiconductor layer intervening a gate insulating film. The device includes a first electrode on the third GaN-based semiconductor layer, a second electrode on the high impurity concentration region, and a third electrode on the opposite side of the first GaN-based semiconductor layer from the second GaN-based semiconductor layer.

Semiconductor device and method of manufacturing the same

GaN based semiconductor device and method of manufacturing the same

In one embodiment, a semiconductor device includes first and second semiconductor layers of a first conductivity type above a substrate via a first film, a first electrode above the second semiconductor layer, and a second electrode disposed on a side of the first electrode or an opposite side of the first electrode with respect to the second semiconductor layer. The device further includes a first pad layer connected to the first electrode, a second pad layer connected to the second electrode and including a first upper portion contacting the second electrode, a second upper portion disposed at a level between upper and lower portions of the substrate, and a third upper portion opposed to the lower portion of the substrate, and a third semiconductor layer of a second conductivity type between the second upper portion of the second pad layer and a lower portion of the first film.

Semiconductor device

In a very high speed bipolar transistor, an n.sup.+ -type GaAs collector layer and an n-type GaAs collector layer are stacked in an intrinsic transistor region, and an i-type GaAs collector layer is formed around the n.sup.+ -type GaAs collector layer and the n-type GaAs collector layer. An n-type GaAs collector layer is formed on the n.sup.+ -type GaAs collector layer such that a part of the n-type GaAs collector layer extends on the i-type GaAs collector layer. A p-type GaAs external base layer is formed outside the n-type GaAs collector layer. A p.sup.+ -type Al.sub.x Ga.sub.l-x As base layer is formed on the n-type GaAs collector layer. An emitter layer is formed such that it is arranged only in the intrinsic transistor region on the p.sup.+ -type Al.sub.x Ga.sub.l-x As base layer and constitutes a heterojunction together with the base layer. Design trade-off between the cutoff frequency and maximum oscillation frequency of the transistor is eliminated.

Bipolar transistor with an improved collector structure

A compound semiconductor device wherein a contact to an n type Al.sub.x Ga.sub.1-x As layer comprises an In.sub.x Ga.sub.1-x As graded-composition layer, an In.sub.x Ga.sub.1-x As contact layer having a constant composition and a metal electrode layer, the In.sub.x Ga.sub.1-x As graded-composition layer is doped with an n type impurity which concentration is higher than a concentration of an impurity activated as n type, whereby, even when a thickness of the In.sub.x Ga.sub.1-x As graded-composition layer is made sufficiently small, a reduction in the carrier concentration of the thin graded-composition layer causes no increase of its resistance and a low-resistance contact is realized.

Growing community of inventors

Ishikawa, Japan

Kunio Tsuda