A nitride-based semiconductor device includes first and second nitride-based semiconductor layers, first electrodes, doped nitride-based semiconductor layers, a second electrode, and gate electrodes. The second nitride-based semiconductor layer is disposed on the first nitride-based semiconductor layer. The first and second nitride-based semiconductor layers collectively have an active portion and an electrically isolating portion surrounding the active portion. The first electrodes are disposed over the second nitride-based semiconductor layer. The first electrodes, doped nitride-based semiconductor layers, the gate electrode, and the second electrode are disposed over the second nitride-based semiconductor layer. Each of the doped nitride-based semiconductor layers has a side surface facing away from the second electrode and spaced apart from the interface.

A semiconductor device includes a first nitride-based semiconductor layer, a second nitride-based semiconductor layer, a pair of first electrodes, a second electrode, a doped nitride-based semiconductor layer, and a pair of gate electrodes. The second nitride-based semiconductor layer is disposed on the first nitride-based semiconductor layer. The first and second nitride-based semiconductor layers collectively have an active portion and an electrically isolating portion that is non-semi-conducting and surrounds the active portion to form an interface therebetween. The first electrodes are disposed over the second nitride-based semiconductor layer. The second electrode are disposed over the second nitride-based semiconductor layer and between the first electrodes. The doped nitride-based semiconductor layer is disposed over the second nitride-based semiconductor layer and between the first electrodes and surrounding the second electrode. The gate electrodes are disposed over the doped nitride-based semiconductor layer and located at opposite sides of the second electrode.

A nitride-based semiconductor device includes a first and second nitride-based semiconductor layers, a doped III-V semiconductor layer, a gate electrode, a first and second source/drain (S/D) electrodes. The doped III-V semiconductor layer is disposed over the second nitride-based semiconductor layer and has first and second current-leakage barrier portions which extends downward from atop surface of the doped III-V semiconductor layer. The gate electrode is disposed above the doped III-V semiconductor layer, in which the gate electrode has a pair of opposite edges between the first and second current-leakage barrier portions. One of the edges of the gate electrode coincides with the first current-leakage barrier portion. The first current-leakage barrier portion is located between the first S/D electrode and the gate electrode. The second current-leakage barrier portion is located between the second S/D electrode and the gate electrode.

A III-nitride-based semiconductor device is provided. The III-nitride semiconductor device includes a silicon substrate having a surface with a periodic array of recesses formed therein. A discontinuous insulating layer is formed within each recess of the periodic array of recesses such that a portion of the silicon substrate surface between adjacent recesses is free from coverage of the discontinuous insulating layer. A first epitaxial III-nitride semiconductor layer is formed over the silicon substrate with the periodic array of recesses and discontinuous insulating layer formed thereon. A second III-nitride semiconductor layer is disposed over the first III-nitride semiconductor layer and has a bandgap greater than a bandgap of the first III-nitride semiconductor layer. At least one source and at least one drain are disposed over the second III-nitride semiconductor layer. A gate is also disposed over the second III-nitride semiconductor layer between the source and the drain.

A semiconductor device, includes an insulating film formed on a substrate; a conductive layer, comprising first and second doped poly-silicon regions and a undoped poly-Si region, formed on the insulating film; a highly doped first conductivity type drain region and a highly doped a first conductivity type source region formed in the first and second doped poly-silicon regions, respectively; and a highly doped second conductivity type gate region formed in the undoped poly-Si region between the highly doped first conductivity type drain region and the highly doped first conductivity type source region. The undoped poly-Si region is disposed closer to the highly doped first conductivity type source region than the highly doped first conductivity type drain region.

A semiconductor device includes a nucleation layer, a buffer layer, a first nitride-based semiconductor layer, a second nitride-based semiconductor layer, S/D electrodes, and a gate electrode. The nucleation layer includes a composition that includes a first element. The buffer layer includes a III-V compound which includes the first element. The buffer layer is disposed on and forms an interface with the nucleation layer. The buffer layer has a concentration of the first element oscillating within the buffer layer, such that the concentration of the first element varies as an oscillating function of a distance within a thickness of the buffer layer. Spacings among adjacent peaks of the oscillating function change from wide to narrow with respect to a first reference point within the buffer layer. The first and second nitride-based semiconductor layer, S/D electrodes, and a gate electrode are disposed on the buffer layer.

A high electron mobility transistor (HEMT) includes an active region, in which a channel is formed, and a field region surrounding the active region. The HEMT may include a channel layer; a barrier layer on the channel layer and configured to induce a two-dimensional electron gas (2DEG) in the channel layer; a source and a drain on the barrier layer in the active region; and a gate on the barrier layer. The gate may protrude from the active region to the field region on the barrier layer. The gate may include a first gate and a second gate. The first gate may be in the active region and the second gate may be in the boundary region between the active region and the field region. A work function of the second gate may be different from a work function of the first gate.

A high electron mobility transistor includes an epitaxial stack on a substrate, a gate structure on the epitaxial stack, a passivation layer on the epitaxial stack and covering the gate structure, and an air gap between the passivation layer and the gate structure.

A gallium nitride based monolithic microwave integrated circuit includes a substrate, a channel layer on the substrate and a barrier layer on the channel layer. A recess is provided in a top surface of the barrier layer. First gate, source and drain electrodes are provided on the barrier layer opposite the channel layer, with a bottom surface of the first gate electrode in direct contact with the barrier layer. Second gate, source and drain electrodes are also provided on the barrier layer opposite the channel layer. A gate insulating layer is provided in the recess in the barrier layer, and the second gate electrode is on the gate insulating layer opposite the barrier layer and extending into the recess. The first gate, source and drain electrodes comprise the electrodes of a depletion mode transistor, and the second gate, source and drain electrodes comprise the electrodes of an enhancement mode transistor.

A control system includes a control unit. When turning a bidirectional switch element ON, the control unit controls the bidirectional switch element to cause a time lag between a first timing and a second timing. The first timing is a timing when a voltage equal to or higher than a threshold voltage is applied to one gate electrode selected from a first gate electrode and a second gate electrode. The one gate electrode is associated with one source electrode selected from a first source electrode and a second source electrode and having a lower potential than the other source electrode. The second timing is a timing when a voltage equal to or higher than a threshold voltage is applied to the other gate electrode associated with the other source electrode having a higher potential than the one source electrode.