A nitride semiconductor device according to the present invention includes a nitride semiconductor layer including an electron transit layer and an electron supply layer which is in contact with the electron transit layer and which has a composition different from that of the electron transit layer, a gate electrode on the nitride semiconductor layer and a gate insulating film between the gate electrode and the nitride semiconductor layer. A region whose depth is 250 nm from an interface between the gate insulating film and the gate electrode includes a region which has a deep acceptor concentration equal to or more than 1.010.sup.16 cm.sup.3.

A normally-off transistor with a high operating voltage is provided. The transistor can include a barrier above the channel and an additional barrier layer located below the channel. A source electrode and a drain electrode are connected to the channel and a gate electrode is connected to the additional barrier layer located below the channel. The bandgap for each of the barrier layers can be larger than the bandgap for the channel. A polarization charge induced at the interface between the additional barrier layer below the channel and the channel depletes the channel. A voltage can be applied to the bottom barrier to induce free carriers into the channel and turn the channel on.

Semiconductor devices and methods of forming the same are provided. A method of the present disclosure includes depositing an aluminum nitride layer over a substrate, treating the aluminum nitride layer to convert a top portion of the aluminum nitride layer to an aluminum oxynitride layer, depositing a III-V semiconductor layer on the aluminum oxynitride layer, and forming a gate structure over the III-V semiconductor layer.

To provide a semiconductor device having improved characteristics. The semiconductor device has a substrate and thereon a buffer layer, a channel layer, a barrier layer, a trench penetrating therethrough and reaching the inside of the channel layer, a gate electrode placed in the trench via a gate insulating film, and drain and source electrodes on the barrier layer on both sides of the gate electrode. The gate insulating film has a first portion made of a first insulating film and extending from the end portion of the trench to the side of the drain electrode and a second portion made of first and second insulating films and placed on the side of the drain electrode relative to the first portion. The on resistance can be reduced by decreasing the thickness of the first portion at the end portion of the trench on the side of the drain electrode.

A compound semiconductor device includes a III-nitride buffer and a III-nitride barrier on the III-nitride buffer. The III-nitride barrier has a different band gap than the III-nitride buffer so that a two-dimensional charge carrier gas channel arises along an interface between the III-nitride buffer and the III-nitride barrier. The compound semiconductor device further includes a source and a drain spaced apart from one another and electrically connected to the two-dimensional charge carrier gas channel, a gate for controlling the two-dimensional charge carrier gas channel between the source and the drain, and a patterned III-nitride back-barrier buried in the III-nitride buffer. The patterned III-nitride back-barrier extends laterally beyond the gate towards the drain and terminates prior to the drain so that the patterned III-nitride back-barrier is laterally spaced apart from the drain by a region of the III-nitride buffer.

The semiconductor device includes: a semiconductor substrate; a first transistor disposed above the semiconductor substrate and including a first source electrode, a first gate region, and a first drain electrode; and a second transistor disposed above the semiconductor substrate and including a second source electrode, a second gate region, and a second drain electrode. The first source electrode, the second gate region, and the second source electrode are substantially at an identical potential. The first drain electrode and the second drain electrode are substantially at an identical potential.

Heterostructure and double-heterostructure trench-gate devices, in which the substrate and/or the body are constructed of a narrower-bandgap semiconductor material than the uppermost portion of the drift region. Fabrication most preferably uses a process where gate dielectric anneal is performed after all other high-temperature steps have already been done.

A method of manufacturing a substrate includes forming a support structure by providing a polycrystalline ceramic core, forming a first adhesion layer coupled to the polycrystalline ceramic core, forming a conductive layer coupled to the first adhesion layer, forming a second adhesion layer coupled to the conductive layer, and forming a barrier layer coupled to the second adhesion layer. The method also includes forming a bonding layer coupled to the support structure, joining a substantially single crystal layer to the bonding layer, wherein the substantially single crystal layer comprises at least one of silicon carbide, sapphire, or gallium nitride, and forming one or more epitaxial III-V layers coupled to the substantially single crystal layer.

A normally-off compound semiconductor transistor includes a heterostructure body and a gate stack on the heterostructure body. The heterostructure body includes a source, a drain spaced apart from the source, and a channel for connecting the source and the drain. The channel includes a first two-dimensional charge carrier gas of a first polarity arising in the heterostructure body due to piezoelectric effects. The gate stack controls the channel in a region of the heterostructure body under the gate stack. The gate stack includes at least one III-nitride material which gives rise to a second two-dimensional charge carrier gas of a second polarity opposite the first polarity in the gate stack or in the heterostructure body under the gate stack due to piezoelectric effects. The second two-dimensional charge carrier gas counter-balances polarization charges in the first two-dimensional charge carrier gas so that the channel is disrupted under the gate stack.

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.