Abstract: A field effect transistor (FET) includes source and drain electrodes, a channel layer, a barrier layer over the channel layer, a passivation layer covering the barrier layer for passivating the barrier layer, a gate electrode extending through the barrier layer and the passivation layer, and a gate dielectric surrounding a portion of the gate electrode that extends through the barrier layer and the passivation layer, wherein the passivation layer is a first material and the gate dielectric is a second material, and the first material is different than the second material.

Abstract: High electron mobility transistors and fabrication processes are presented in which a barrier material layer of uniform thickness is provided for threshold voltage control under an enhanced channel charge inducing material layer (ECCIML) in source and drain regions with the ECCIML layer removed in the gate region.

Abstract: A III-N device is described with a III-N layer, an electrode thereon, a passivation layer adjacent the III-N layer and electrode, a thick insulating layer adjacent the passivation layer and electrode, a high thermal conductivity carrier capable of transferring substantial heat away from the III-N device, and a bonding layer between the thick insulating layer and the carrier. The bonding layer attaches the thick insulating layer to the carrier. The thick insulating layer can have a precisely controlled thickness and be thermally conductive.

Abstract: There is provided a semiconductor device having a High Electron Mobility Transistor (HEMT) structure allowing for enhanced performance and a method of manufacturing the same. The semiconductor device includes a base substrate; a semiconductor layer provided on the base substrate; a source electrode, a gate electrode and a drain electrode provided on the semiconductor layer to be spaced apart from one another; and an ohmic-contact layer partially provided at an interface between the drain electrode and the semiconductor layer.

Abstract: A method of fabricating a multi-layer structure for a power transistor device includes performing, within a reaction chamber, a nitrogen plasma strike, resulting in the formation of a nitride layer directly on a nitride-based active semiconductor layer. A top surface of the nitride layer is then exposed to a second source. A subsequent nitrogen-oxygen plasma strike results in the formation of an oxy-nitride layer directly on the nitride layer. The nitride layer comprises a passivation layer and the oxy-nitride layer comprises a gate dielectric of the power transistor device.

Abstract: An integrated circuit structure includes a substrate and a first and a second plurality of III-V semiconductor layers. The first plurality of III-V semiconductor layers includes a first bottom barrier over the substrate; a first channel layer over the first bottom barrier; and a first top barrier over the first channel layer. A first field-effect transistor (FET) includes a first channel region, which includes a portion of the first channel layer. The second plurality of III-V semiconductor layers is over the first plurality of III-V semiconductor layers and includes a second bottom barrier; a second channel layer over the second bottom barrier; and a second top barrier over the second channel layer. A second FET includes a second channel region, which includes a portion of the second channel layer.

Abstract: A semiconductor device and a fabrication method of the semiconductor device, the semiconductor device including: a substrate; a nitride based compound semiconductor layer placed on the substrate and doped with a first transition metal atom; an aluminum gallium nitride layer (AlxGa1-xN) (where 0.1<=x<=1) placed on the nitride based compound semiconductor layer; a nitride based compound semiconductor layer placed on the aluminum gallium nitride layer (AlxGa1-xN) (where 0.1<=x<=1) and doped with a second transition metal atom; an aluminum gallium nitride layer (AlyGa1-yN) (where 0.1<=y<=1) placed on the nitride based compound semiconductor layer doped with the second transition metal atom; and a gate electrode, a source electrode, and a drain electrode which are placed on the aluminum gallium nitride layer (AlyGa1-yN) (where 0.1<=y<=1).

Abstract: An n-layer is arranged above a substrate, which can be GaAs, and a p-layer (4) is arranged on the n-layer. The p-layer is separated by a gate electrode into two separate portions forming source and drain. The gate electrode is insulated from the semiconductor material by a gate dielectric. Source/drain contacts are electrically conductively connected with the portions of the p-layer.

Abstract: A HEMT comprising a plurality of active semiconductor layers formed on a substrate. Source electrode, drain electrode, and gate are formed in electrical contact with the plurality of active layers. A spacer layer is formed on at least a portion of a surface of said plurality of active layers and covering the gate. A field plate is formed on the spacer layer and electrically connected to the source electrode, wherein the field plate reduces the peak operating electric field in the HEMT.

Abstract: A dual-gate normally-off nitride transistor that includes a first gate structure formed between a source electrode and a drain electrode for controlling a normally-off channel region of the dual-gate normally-off nitride transistor. A second gate structure is formed between the first gate structure and the drain electrode for modulating a normally-on channel region underneath the second gate structure. The magnitude of the threshold voltage of the second gate structure is smaller than the drain breakdown of the first gate structure for proper operation of the dual-gate normally-off nitride transistor.

Abstract: An embodiment of a compound semiconductor device includes: a substrate; an electron channel layer and an electron supply layer formed over the substrate; a gate electrode, a source electrode and a drain electrode formed on or above the electron supply layer; and a p-type semiconductor layer formed between the electron supply layer and the gate electrode. The p-type semiconductor layer contains, as a p-type impurity, an element same as that being contained in at least either of the electron channel layer and the electron supply layer.

Abstract: A method for fabricating an electronic device, comprising wafer bonding a first semiconductor material to a III-nitride semiconductor, at a temperature below 550° C., to form a device quality heterojunction between the first semiconductor material and the III-nitride semiconductor, wherein the first semiconductor material is different from the III-nitride semiconductor and is selected for superior properties, or preferred integration or fabrication characteristics in the injector region as compared to the III-nitride semiconductor.

Abstract: A method for fabricating a gate structure for a field effect transistor having a buffer layer on a substrate, a channel layer and a barrier layer over the channel layer includes forming a gate including silicon, forming first sidewalls of a first material on either side and adjacent to the gate, selectively etching into the buffer layer to form a mesa for the field effect transistor, depositing a material layer over the mesa, planarizing the material layer over the mesa to form a planarized surface such that a top of the gate, tops of the first sidewalls, and a top of the material layer over the mesa are on the same planarized surface, depositing metal on the planzarized surface, annealing to form the gate into a metal silicided gate, and etching to remove excess non-silicided metal.

Abstract: The present invention relates to an enhancement normally off nitride semiconductor device and a method of manufacturing the same. The method includes the steps of: forming a buffer layer on a substrate; forming a first nitride semiconductor layer on the buffer layer; forming a second nitride semiconductor layer on the first nitride semiconductor layer; etching a gate region above the second nitride semiconductor layer up to a predetermined depth of the first nitride semiconductor layer; forming an insulating film on the etched region and the second nitride semiconductor layer; patterning a source/drain region, etching the insulating film in the source/drain region, and forming electrodes in the source/drain region; and forming a gate electrode on the insulating film in the gate region. In this manner, the present invention provides a method of easily implementing a normally off enhancement semiconductor device by originally blocking 2DEG which is generated under a gate region.

Abstract: A nitride semiconductor device includes: a main semiconductor region comprising a first nitride semiconductor layer having a first band gap, and a second nitride semiconductor layer having a second band gap larger than the first band gap, a heterojunction being formed between the first nitride semiconductor layer and a the second nitride semiconductor layer such that two-dimensional electron gas layer can be caused inside the first nitride semiconductor layer based on the heterojunction; a source electrode formed on the main semiconductor region; a drain electrode formed on the main semiconductor region and separated from the source electrode; a third nitride semiconductor layer formed on the first nitride semiconductor layer and between the source electrode and the drain electrode; and a gate electrode formed on the third nitride semiconductor layer. The third nitride semiconductor layer has a third band gap smaller than the first band gap.

Abstract: A semiconductor device includes: substrate region; a gate electrode, a source electrode, and a drain electrode which are placed on a first surface of the substrate regions; an active area between gate and source placed between the gate electrode and the source electrode; an active area between gate and drain placed between the gate electrode and the drain electrode; an active area placed on the substrate region of the underneath part of the gate electrode, the source electrode, and the drain electrode; and a non-active area placed adjoining the active area, the active area between gate and source, and the active area between gate and drain. Furthermore, width WA1 of the active area between gate and source is wider than width WA2 of the active area between gate and drain. Channel resistance of an active area between source and gate placed between a gate electrode and a source electrode is reduced, and high-frequency performance is provided.

Abstract: The present disclosure provides a semiconductor device. The semiconductor device includes a silicon substrate. A first III-V compound layer is disposed over the silicon substrate. A second III-V compound layer is disposed over the first III-V compound layer. The semiconductor device includes a transistor disposed over the first III-V compound layer and partially in the second III-V compound layer. The semiconductor device includes a diode disposed in the silicon substrate. The semiconductor device includes a via coupled to the diode and extending through at least the first III-V compound layer. The via is electrically coupled to the transistor or disposed adjacent to the transistor.

Abstract: In general, in a semiconductor active element such as a normally-off JFET based on SiC in which an impurity diffusion speed is significantly lower than in silicon, gate regions are formed through ion implantation into the side walls of trenches formed in source regions. However, to ensure the performance of the JFET, it is necessary to control the area between the gate regions thereof with high precision. Besides, there is such a problem that, since a heavily doped PN junction is formed by forming the gate regions in the source regions, an increase in junction current cannot be avoided. The present invention provides a normally-off power JFET and a manufacturing method thereof and forms the gate regions according to a multi-epitaxial method which repeats a process including epitaxial growth, ion implantation, and activation annealing a plurality of times.

Abstract: A method of manufacturing a semiconductor device, in which a second semiconductor layer of AlxGa1-x-yInyN (wherein x, y, and x+y satisfy x>0, y?0, and x+y?1, respectively) on a first semiconductor layer of GaN by hetero-epitaxial growth using a MOCVD method, the method including the steps of: (a) supplying N source gas and Ga source gas to form the first semiconductor layer; (b) supplying the N source gas without supplying the Ga source gas and Al source gas, after step (a); (c) supplying the N source gas and the Al source gas without supplying the Ga source gas, after step (b); and (d) supplying the N source gas, the Ga source gas and the Al source gas to form the second semiconductor layer, after step (c).

Abstract: A semiconductor structure includes a first III-V compound layer. A second III-V compound layer is disposed on the first III-V compound layer and different from the first III-V compound layer in composition. A carrier channel is located between the first III-V compound layer and the second III-V compound layer. A source feature and a drain feature are disposed on the second III-V compound layer. A gate electrode is disposed over the second III-V compound layer between the source feature and the drain feature. Two slanted field plates are disposed on the two side walls of the combined opening of the opening in a protection layer and the opening in a dielectric cap layer disposed on the second III-V compound layer.

Abstract: A semiconductor device includes a substrate, a carrier transit layer disposed above the substrate, a compound semiconductor layer disposed on the carrier transit layer, a source electrode disposed on the compound semiconductor layer, a first groove disposed from the back of the substrate up to the inside of the carrier transit layer while penetrating the substrate, a drain electrode disposed in the inside of the first groove, a gate electrode located between the source electrode and the first groove and disposed on the compound semiconductor layer, and a second groove located diagonally under the source electrode and between the source electrode and the first groove and disposed from the back of the substrate up to the inside of the carrier transit layer while penetrating the substrate.

Abstract: A method of manufacturing a nitride semiconductor device including: forming a nitride semiconductor layer over a substrate wherein the nitride semiconductor layer has a 2DEG channel inside; forming a drain electrode in ohmic contact with the nitride semiconductor layer and a source electrode spaced apart from the drain electrode, in Schottky contact with the nitride semiconductor layer, wherein the source electrode has an ohmic pattern in ohmic contact with the nitride semiconductor layer inside; forming a dielectric layer on the nitride semiconductor layer between the drain electrode and the source electrode and on at least a portion of the source electrode; and forming a gate electrode on the dielectric layer to be spaced apart from the drain electrode, wherein a portion of the gate electrode is formed on the dielectric layer over a drain-side edge portion of the source electrode.

Abstract: A method of making a high-electron mobility transistor (HEMT) includes forming an unintentionally doped gallium nitride (UID GaN) layer over a silicon substrate, a donor-supply layer over the UID GaN layer, a gate, a passivation layer over the gate and portions of the donor-supply layer, an ohmic source structure and an ohmic drain structure over the donor-supply layer and portions of the passivation layer. The source structure includes a source contact portion and an overhead portion. The overhead portion overlaps the passivation layer between the source contact portion and the gate, and may overlap a portion of the gate and a portion of the passivation layer between the gate and the drain structure.

Abstract: A semiconductor device includes a substrate; a nitride based compound semiconductor layer placed on the substrate; an active area which is placed on the nitride based compound semiconductor layer, and is composed of an aluminum gallium nitride layer (AlxGa1-xN) (where 0.1<=x<=1); an isolation region which performs isolation of the active area mutually; a gate electrode, a source electrode, and a drain electrode which have been placed on the active area surrounded by the isolation region; and a trench region formed by etching for a part of the active area under the gate electrode. The semiconductor device is highly reliable, high performance and high power and a fabrication method for the same is also provided.

Abstract: A semiconductor structure includes a first III-V compound layer. A second III-V compound layer is disposed on the first III-V compound layer and different from the first III-V compound layer in composition. A carrier channel is located between the first III-V compound layer and the second III-V compound layer. A source feature and a drain feature are disposed on the second III-V compound layer. A gate electrode is disposed over the second III-V compound layer between the source feature and the drain feature. A carrier channel depleting layer is disposed on the second III-V compound layer. The carrier channel depleting layer is deposited using plasma and a portion of the carrier channel depleting layer is under at least a portion of the gate electrode.

Abstract: A method for fabricating a semiconductor device is disclosed. The method includes sequentially forming a first semiconductor layer, a second semiconductor layer and a semiconductor cap layer containing a p-type impurity element on a substrate, forming a dielectric layer having an opening after the forming of the semiconductor cap layer, forming a third semiconductor layer containing a p-type impurity element on the semiconductor cap layer exposed from the opening of the dielectric layer, and forming a gate electrode on the third semiconductor layer.

Abstract: According to an example embodiment, a power device includes a substrate, a nitride-containing stack on the substrate, and an electric field dispersion unit. Source, drain, and gate electrodes are on the nitride-containing stack. The nitride-containing stack includes a first region that is configured to generate a larger electric field than that of a second region of the nitride-containing stack. The electric field dispersion unit may be between the substrate and the first region of the nitride-containing stack.

Abstract: A compound semiconductor epitaxial substrate having a pseudomorphic high electron mobility field effect transistor structure including an InGaAs layer as a strained channel layer and an AlGaAs layer containing n type impurities as a front side electron-donating layer, wherein said substrate contains an InGaP layer in an orderly state on the front side of the above described InGaAs layer as the strained channel layer.

Abstract: A method of fabricating a GaN HEMT includes growing a first epitaxial layer on a substrate, growing a second epitaxial layer on the first epitaxial layer, growing a third epitaxial layer on the second epitaxial layer, depositing a first dielectric film on the third epitaxial layer, using dielectric films to form a first sidewall dielectric spacer, forming a sidewall gate adjacent the first sidewall dielectric spacer. The sidewall gate may be made to be less than 50 nm in length.

Abstract: Novel silicon dioxide and silicon nitride deposition methods are generally disclosed. In one embodiment, the method includes depositing silicon on the surface of a substrate having a temperature of between about 65° C. and about 350° C. The heated substrate is exposed to a silicon source that is substantially free from an oxidizing agent. The silicon on the surface is then oxidized with an oxygen source that is substantially free from a silicon source. As a result of oxidizing the silicon, a silicon oxide layer forms on the surface of the substrate. Alternatively, or in additionally, a nitrogen source can be provided to produce silicon nitride on the surface of the substrate.

Abstract: A III-V-group compound semiconductor device includes a substrate, a channel layer provided over the substrate, a barrier layer provided on the channel layer so as to form a hetero-interface, a plurality of electrodes provided on the barrier layer, an insulator layer provided to cover an entire upper surface of the barrier layer except for at least partial regions of the electrodes, and a hydrogen-absorbing layer stacked on the insulator layer or an integrated layer in which an hydrogen-absorbing layer is integrated with the insulator layer.

Abstract: A dual-gate normally-off nitride transistor that includes a first gate structure formed between a source electrode and a drain electrode for controlling a normally-off channel region of the dual-gate normally-off nitride transistor. A second gate structure is formed between the first gate structure and the drain electrode for modulating a normally-on channel region underneath the second gate structure. The magnitude of the threshold voltage of the second gate structure is smaller than the drain breakdown of the first gate structure for proper operation of the dual-gate normally-off nitride transistor.

Abstract: An enhancement mode III-Nitride device has a floating gate spaced from a drain electrode which is programmed by charges injected into the floating gate to form a permanent depletion region which interrupts the 2-DEG layer beneath the floating gate. A conventional gate is formed atop the floating gate and is insulated therefrom by a further dielectric layer. The device is a normally off E mode device and is turned on by applying a positive voltage to the floating gate to modify the depletion layer and reinstate the 2-DEG layer. The device is formed by conventional semiconductor fabrication techniques.

Abstract: Methods of achieving high breakdown voltages in semiconductor devices by suppressing the surface flashover using high dielectric strength insulating encapsulation material are generally described. In one embodiment of the present invention, surface flashover in AlGaN/GaN heterostructure field-effect transistors (HFETs) is suppressed by using high dielectric strength insulating encapsulation material. Surface flashover in as-fabricated III-Nitride based HFETs limits the operating voltages at levels well below the breakdown voltages of GaN.

Abstract: A compound semiconductor device is provided with a substrate, an AlN layer formed over the substrate, an AlGaN layer formed over the AlN layer and larger in electron affinity than the AlN layer, another AlGaN layer formed over the AlGaN layer and smaller in electron affinity than the AlGaN layer. Furthermore, there are provided an i-GaN layer formed over the latter AlGaN layer, and an i-AlGaN layer and an n-AlGaN layer formed over the i-GaN layer.

Abstract: A MOSFET driver compatible JFET device is disclosed. The JFET device can include a gate contact, a drain contact, and a source contact. The JFET device can further include a first gate region of semiconductor material adjacent the gate contact and a second region of semiconductor material adjacent the first gate region. The first gate region and the second gate region can form a first p-n junction between the first gate region and the second gate region. The JFET device can further include a channel region of semiconductor material adjacent the source contact. The channel region and the second gate region can form a second p-n junction between the second gate region and the channel region.

Abstract: A method of manufacturing a High Electron Mobility Transistor (HEMT) may include forming first and second material layers having different lattice constants on a substrate, forming a source, a drain, and a gate on the second material layer, and changing the second material layer between the gate and the drain into a different material layer, or changing a thickness of the second material layer, or forming a p-type semiconductor layer on the second material layer. The change in the second material layer may occur in an entire region of the second material layer between the gate and the drain, or only in a partial region of the second material layer adjacent to the gate. The p-type semiconductor layer may be formed on an entire top surface of the second material layer between the gate and the drain, or only on a partial region of the top surface adjacent to the gate.

Abstract: A method of producing a semiconductor device, includes: forming a semiconductor layer on a substrate; forming an a recess in the semiconductor layer by dry etching with a gas containing fluorine components, the recess having an opening portion on the surface of the semiconductor layer; forming a fluorine-containing region by heating the semiconductor layer and thus diffusing, into the semiconductor layer, the fluorine components attached to side surfaces and a bottom surface of the recess; forming an insulating film on an inner surface of the recess and on the semiconductor layer; and forming an electrode on the insulating film in a region in which the recess is formed.

Abstract: A sealed semiconductor device having reduced delamination of the sealing layer in high temperature, high humidity conditions is disclosed. The semiconductor device includes a substrate and a stack of device layers on the substrate sealed with a sealing layer. The upper surface of a street area of the substrate is oxidized so that the oxidized region extends under the sealing layer. The presence of the oxidized region of the upper surface of the substrate helps reduce the delamination, because the oxidized surface does not react with water to the same extent as a non-oxidized surface. The semiconductor devices remain sealed after dicing through the street area because the oxidized surface does not delaminate.

Abstract: A nitride semiconductor device 2 comprises a nitride semiconductor layer 10. A gate insulating film 16 is formed on the surface of the nitride semiconductor layer 10. The gate insulating film 16 includes a portion composed of an aluminum nitride film 15 and a portion composed of an insulating material 14 that contains at least one of oxygen or silicon. A region W2 of the nitride semiconductor layer 10 facing the aluminum nitride film 15 is included in a region W1 of the nitride semiconductor layer 10 facing a gate electrode 18. The nitride semiconductor device 2 may further comprise a nitride semiconductor lower layer 8. The nitride semiconductor layer 10 may be stacked on the surface of the nitride semiconductor lower layer 8. The nitride semiconductor layer 10 may have a larger band gap than that of the nitride semiconductor lower layer 8 and have a heterojunction formed there between.

Abstract: A compound semiconductor device includes a compound semiconductor substrate; epitaxially grown layers formed over the compound semiconductor substrate and including a channel layer and a resistance lowering cap layer above the channel layer; source and drain electrodes in ohmic contact with the channel layer; recess formed by removing the cap layer between the source and drain electrodes; a first insulating film formed on an upper surface of the cap layer and having side edges at positions retracted from edges, or at same positions as the edges of the cap layer in a direction of departing from the recess; a second insulating film having gate electrode opening and formed covering a semiconductor surface in the recess and the first insulating film; and a gate electrode formed on the recess via the gate electrode opening.

Abstract: A III-nitride power device that includes a Schottky electrode surrounding one of the power electrodes of the device.

Abstract: A method for fabricating a transistor and the resulting transistor is disclosed. The method generally includes steps (A) to (E). Step (A) may form a high mobility layer. The high mobility layer is generally configured to carry a two-dimensional electron gas. Step (B) may form a planar layer on the high mobility layer. Step (C) may form a barrier layer on the planar layer. Step (D) may form a doped layer on the barrier layer. The doped layer is generally a low bandgap III-V semiconductor. Step (E) may form a gate in contact with the doped layer. The gate may be separated from both a source and a drain by corresponding ungated recess regions. The high mobility layer, the planar layer, the barrier layer, the doped layer, the source, the gate and the drain are generally configured as a pseudomorphic high electron mobility transistor.

Abstract: A III-nitride device includes a recessed electrode to produce a nominally off, or an enhancement mode, device. By providing a recessed electrode, a conduction channel formed at the interface of two III-nitride materials is interrupted when the electrode contact is inactive to prevent current flow in the device. The electrode can be a schottky contact or an insulated metal contact. Two ohmic contacts can be provided to form a rectifier device with nominally off characteristics. The recesses formed with the electrode can have sloped sides. The electrode can be formed in a number of geometries in conjunction with current carrying electrodes of the device. A nominally on device, or pinch resistor, is formed when the electrode is not recessed. A diode is also formed by providing non-recessed ohmic and schottky contacts through an insulator to an AlGaN layer.

Abstract: Various embodiments of the disclosure include the formation of enhancement-mode (e-mode) gate injection high electron mobility transistors (HEMT). Embodiments can include GaN, AlGaN, and InAlN based HEMTs. Embodiments also can include self-aligned P-type gate and field plate structures. The gates can be self-aligned to the source and drain, which can allow for precise control over the gate-source and gate-drain spacing. Additional embodiments include the addition of a GaN cap structure, an AlGaN buffer layer, AlN, recess etching, and/or using a thin oxidized AlN layer. In manufacturing the HEMTs according to present teachings, selective epitaxial growth (SEG) and epitaxial lateral overgrowth (ELO) can both be utilized to form gates.

Abstract: A light emitting element array including an active layer commonly used for light emitting element regions, carrier injection layers which are electrically isolated from each other and which are provided in the respective light emitting element regions, and a resistive layer which has a resistance higher than that of the carrier injection layers and which is provided between the active layer and the carrier injection layers.

Abstract: A semiconductor device includes: a semiconductor base; a hetero semiconductor region which is in contact with the semiconductor base and which has a band gap different from that of the semiconductor base; a first electrode connected to the hetero semiconductor region; and a second electrode forming an ohmic contact to the semiconductor base. The hetero semiconductor region includes a laminated hetero semiconductor region formed by laminating a plurality of semiconductor layers in which crystal alignment is discontinuous at a boundary between at least two layers.

Abstract: A semiconductor device 1 includes a substrate 2 having on a main surface thereof a central area and a peripheral area which surrounds the central area and is exposed, a semiconductor layer 4 which is formed on the main surface of the substrate 2, is made of a material harder than the substrate 2, is in the shape of a mesa, and has a steep side over the exposed peripheral area, and an insulating film 12S provided on a side surface of the semiconductor layer 4.

Abstract: A semiconductor device includes a substrate; a nitride based compound semiconductor layer placed on the substrate; an active area which is placed on the nitride based compound semiconductor layer, and is composed of an aluminum gallium nitride layer (AlxGa1-xN) (where 0.1<=x<=1); an isolation region which performs isolation of the active area mutually; a gate electrode, a source electrode, and a drain electrode which have been placed on the active area surrounded by the isolation region; and a trench region formed by etching for a part of the active area under the gate electrode. The semiconductor device is highly reliable, high performance and high power and a fabrication method for the same is also provided.

Abstract: A field-effect transistor includes a semi-insulating substrate, a source electrode, a drain electrode, a gate electrode, the electrodes being provided on the semi-insulating substrate, and a buried gate region which is provided under the gate electrode and in which an impurity is doped, wherein a concave slit is provided in the semi-insulating substrate, the slit being located between the gate electrode and the drain electrode and being adjacent to the buried gate region at the side of the drain electrode.