A method includes: providing a Group III nitride-based substrate having a first major surface and a doped Group III nitride region; forming a first passivation layer configured as a hydrogen diffusion barrier on the first major surface; forming a first opening in the first passivation layer and exposing at least a portion of the doped Group III nitride region from the first passivation layer; activating a first doped Group III nitride region whilst the first passivation layer is located on the first major surface and the doped Group III nitride region is at least partly exposed from the first passivation layer; forming a second passivation layer on the first passivation layer and on the doped Group III nitride region; forming a second opening in the first and second passivation layers and exposing a portion of the doped Group III nitride region; and forming a contact in the second opening.

A method for manufacturing nitride semiconductor device includes a second step of forming, on a gate layer material film, a gate electrode film that is a material film of a gate electrode, a third step of selectively etching the gate electrode film to form the gate electrode 22 of a ridge shape, and a fourth step of selectively etching the gate layer material film to form a semiconductor gate layer 21 of a ridge shape with the gate electrode 22 disposed at a width intermediate portion of a front surface thereof. The third step includes a first etching step for forming a first portion 22A from an upper end to a thickness direction intermediate portion of the gate electrode 22 and a second etching step being a step differing in etching condition from the first etching step and being for forming a remaining second portion 22B of the gate electrode.

A semiconductor device including a group III-V barrier and a method of manufacturing the semiconductor device, the semiconductor device including: a substrate, insulation layers formed to be spaced apart on the substrate, a group III-V material layer for filling the space between the insulation layers and having a portion protruding higher than the insulation layers, a barrier layer for covering the side and upper surfaces of the protruding portion of the group III-V material layer and having a bandgap larger than that of the group III-V material layer, a gate insulation film for covering the surface of the barrier layer, a gate electrode formed on the gate insulation film, and source and drain electrodes formed apart from the gate electrode. The overall composition of the group III-V material layer is uniform. The barrier layer may include a group III-V material for forming a quantum well.

Techniques related to III-N transistors having enhanced breakdown voltage, systems incorporating such transistors, and methods for forming them are discussed. Such transistors include a hardmask having an opening over a substrate, a source, a drain, and a channel between the source and drain, and a portion of the source or the drain disposed over the opening of the hardmask.

High electron mobility transistors (HEMT) exhibiting dual depletion and methods of manufacturing the same. The HEMT includes a source electrode, a gate electrode and a drain electrode disposed on a plurality of semiconductor layers having different polarities. A dual depletion region exists between the source electrode and the drain electrode. The plurality of semiconductor layers includes an upper material layer, an intermediate material layer and a lower material layer, and a polarity of the intermediate material layer is different from polarities of the upper material layer and the lower material layer.

Transistors or transistor layers include an InAlN and AlGaN bi-layer capping stack on a 2DEG GaN channel, such as for GaN MOS structures on Si substrates. The GaN channel may be formed in a GaN buffer layer or stack, to compensate for the high crystal structure lattice size and coefficient of thermal expansion mismatch between GaN and Si. The bi-layer capping stack an upper InAlN layer on a lower AlGaN layer to induce charge polarization in the channel, compensate for poor composition uniformity (e.g., of Al), and compensate for rough surface morphology of the bottom surface of the InAlN material. It may lead to a sheet resistance between 250 and 350 ohms/sqr. It may also reduce bowing of the GaN on Si wafers during growth of the layer of InAlN material, and provide a AlGaN setback layer for etching the InAlN layer in the gate region.

III-N transistors with epitaxial semiconductor heterostructures having steep subthreshold slope are described. In embodiments, a III-N HFET employs a gate stack with balanced and opposing III-N polarization materials. Overall effective polarization of the opposing III-N polarization materials may be modulated by an external field, for example associated with an applied gate electrode voltage. In embodiments, polarization strength differences between the III-N materials within the gate stack are tuned by composition and/or film thickness to achieve a desired transistor threshold voltage (V.sub.t). With polarization strengths within the gate stack balanced and opposing each other, both forward and reverse gate voltage sweeps may generate a steep sub-threshold swing in drain current as charge carriers are transferred to and from the III-N polarization layers and the III-N channel semiconductor.

According to this GaN-based HFET, resistivity of a semi-insulating film forming a gate insulating film is 3.910.sup.9cm. The value of this resistivity is a value derived when the current density is 6.2510.sup.4 (A/cm.sup.2). By inclusion of the gate insulating film by a semi-insulating film having a resistivity =3.910.sup.9cm, a withstand voltage of 1000 V can be obtained. Meanwhile, the withstand voltage abruptly drops as the resistivity of the gate insulating film exceeds 1 10.sup.11cm, and the gate leak current increases when the resistivity of the gate insulating film drops below 1 10.sup.7cm.

Embodiments include epitaxial semiconductor stacks for reduced defect densities in III-N device layers grown over non-III-N substrates, such as silicon substrates. In embodiments, a metamorphic buffer includes an Al.sub.xIn.sub.1-xN layer lattice matched to an overlying GaN device layers to reduce thermal mismatch induced defects. Such crystalline epitaxial semiconductor stacks may be device layers for HEMT or LED fabrication, for example. System on Chip (SoC) solutions integrating an RFIC with a PMIC using a transistor technology based on group III-nitrides (III-N) capable of achieving high F.sub.t and also sufficiently high breakdown voltage (BV) to implement high voltage and/or high power circuits may be provided on the semiconductor stacks in a first area of the silicon substrate while silicon-based CMOS circuitry is provided in a second area of the substrate.

A method for manufacturing a HEMT transistor comprising the steps of: providing a wafer comprising a semiconductor body including a heterojunction structure formed by semiconductor materials that include elements of Groups III-V of the Periodic Table, and a dielectric layer on the semiconductor body; etching selective portions of the wafer, thus exposing a portion of the heterojunction structure; forming an interface layer by a surface reconstruction process, of a semiconductor compound formed by elements of Groups III-V of the Periodic Table, in the exposed portion of the heterojunction structure; and forming a gate electrode, including a gate dielectric and a gate conductive region, on said interface layer.