Abstract: In a vertical-type semiconductor device, a method of manufacturing the same and a method of operating the same, the vertical-type semiconductor device includes a single-crystalline semiconductor pattern having a pillar shape provided on a substrate, a gate surrounding sidewalls of the single-crystalline semiconductor pattern and having an upper surface lower than an upper surface of the single-crystalline semiconductor pattern, a mask pattern formed on the upper surface of the gate, the mask pattern having an upper surface coplanar with the upper surface of the single-crystalline semiconductor pattern, a first impurity region in the substrate under the single-crystalline semiconductor pattern, and a second impurity region under the upper surface of the single-crystalline semiconductor pattern. The vertical-type pillar transistor formed in the single-crystalline semiconductor pattern may provide excellent electrical properties.

Abstract: A downsized semiconductor device having an excellent reverse characteristic, and a method of manufacturing the semiconductor device is sought to improve. The semiconductor device comprises a semiconductor body having a polygonal contour. An active area is formed in the semiconductor body. An EQR electrode is formed so as to surround the active area and to have curved portions of the EQR electrode along the corners of the semiconductor body. An interlayer insulating film is formed to cover the active area and the EQR electrode. The EQR electrode is embedded in the interlayer insulating film around the active area. EQR contacts are in contact with the curved portions of the EQR electrode and the semiconductor body outside the curved portions, and have at least side walls covered with the interlayer insulating film.

Abstract: A FinFET includes a substrate, a fin structure on the substrate, a source in the fin structure, a drain in the fin structure, a channel in the fin structure between the source and the drain, a gate dielectric layer over the channel, and a gate over the gate dielectric layer. At least one of the source and the drain includes a bottom SiGe layer.

Abstract: The present disclosure relates to the fabrication of microelectronic devices having at least one negative differential resistance device formed therein. In at least one embodiment, the negative differential resistance devices may be formed utilizing quantum wells. Embodiments of negative differential resistance devices of present description may achieve high peak drive current to enable high performance and a high peak-to-valley current ratio to enable low power dissipation and noise margins, which allows for their use in logic and/or memory integrated circuitry.

Abstract: A field effect transistor, in accordance with one embodiment, includes a metal-oxide-semiconductor field effect transistor (MOSFET) having a junction field effect transistor (JFET) embedded as a body diode.

Abstract: A gate stack including a gate dielectric and a gate electrode is formed over at least one compound semiconductor fin provided on an insulating substrate. The at least one compound semiconductor fin is thinned employing the gate stack as an etch mask. Source/drain extension regions are epitaxially deposited on physically exposed surfaces of the at least one semiconductor fin. A gate spacer is formed around the gate stack. A raised source region and a raised drain region are epitaxially formed on the source/drain extension regions. The source/drain extension regions are self-aligned to sidewalls of the gate stack, and thus ensure a sufficient overlap with the gate electrode. Further, the combination of the source/drain extension regions and the raised source/drain regions provides a low-resistance path to the channel of the field effect transistor.

Abstract: Semiconductor devices are provided. The semiconductor device includes word lines on a semiconductor substrate, common gates connected to each of the word lines and vertically disposed in the semiconductor substrate, buried bit lines intersecting the word lines at a non-right angle in a plan view, and a pair of vertical transistors sharing each of the common gates. The pair of vertical transistors are disposed at both sides of one of the word lines, respectively. Further, the pair of vertical transistors are electrically connected to two adjacent ones of the buried bit lines, respectively. Electronic systems including the semiconductor device and related methods are also provided.

Abstract: A field-effect semiconductor device is provided. The field-effect semiconductor device includes a semiconductor body with a first surface defining a vertical direction. In a vertical cross-section the field-effect semiconductor device further includes a vertical trench extending from the first surface into the semiconductor body. The vertical trench includes a field electrode, a cavity at least partly surrounded by the field electrode, and an insulation structure substantially surrounding at least the field electrode. Further, a method for producing a field-effect semiconductor device is provided.

Abstract: A phase-change random access memory (PCRAM) device includes a semiconductor substrate; switching elements formed on the semiconductor substrate; a plurality of phase-change structures formed on the switching elements; and heat absorption layers buried between the plurality of phase-change structures, wherein the plurality of phase-change structures are insulated from the heat absorption layers.

Abstract: It is an object to provide a semiconductor device in which a short-channel effect is suppressed and miniaturization is achieved, and a manufacturing method thereof. A trench is formed in an insulating layer and impurities are added to an oxide semiconductor film in contact with an upper end corner portion of the trench, whereby a source region and a drain region are formed. With the above structure, miniaturization can be achieved. Further, with the trench, a short-channel effect can be suppressed setting the depth of the trench as appropriate even when a distance between a source electrode layer and a drain electrode layer is shortened.

Abstract: Provided is a power semiconductor device including a semiconductor substrate, in which a current flows in a thickness direction of the semiconductor substrate. The semiconductor substrate includes a resistance control structure configured so that a resistance to the current becomes higher in a central portion of the semiconductor substrate than a peripheral portion of the semiconductor substrate.

Abstract: A device includes a wafer substrate, a conical frustum structure formed in the wafer substrate, and a gate all-around (GAA) structure circumscribing the middle portion of the conical frustum structure. The conical frustum structure includes a drain formed at a bottom portion of the conical frustum, a source formed at a top portion of the vertical conical frustum, and a channel formed at a middle portion of the conical frustum connecting the source and the drain. The GAA structure overlaps with the source at one side of the GAA structure, crosses over the channel, and overlaps with the drain at another side of the GAA structure.

Abstract: An electrical circuit includes first and second transistors. Each transistor includes a substrate and, positioned thereon, a first electrically conductive material layer including a reentrant profile functioning as a gate. First and second discrete portions of a second electrically conductive material layer are in contact with first and second portions, respectively, of a semiconductor material layer in contact with an electrically insulating material layer, both of which conform to the reentrant profile. The first and second discrete portions are source/drain and drain/source electrodes of the first and second transistors, respectively. A third electrically conductive material layer, in contact with a third portion of the semiconductor material layer, is positioned over the gate, but is not in electrical contact with it.

Abstract: A method is provided for fabricating a vertical insulated gate transistor. A horizontal isolation region is formed in a substrate to separate and electrically isolate upper and lower portions of the substrate. A vertical semiconductor pillar with one or more flanks and a cavity is formed so as to rest on the upper portion, and a dielectrically isolated gate is formed so as to include an internal portion within the cavity and an external portion resting on the flanks and on the upper portion. One or more internal walls of the cavity are coated with an isolating layer and the cavity is filled with a gate material so as to form the internal portion of the gate within the cavity and the external portion of the gate that rests on the flanks, and to form two connecting semiconductor regions extending between source and drain regions of the transistor.

Abstract: A vertical conduction electronic power device includes respective gate, source and drain areas in an epitaxial layer arranged on a semiconductor substrate. The respective gate, source and drain metallizations may be formed by a first metallization level. Corresponding gate, source and drain terminals or pads may be formed by a second metallization level. The power device is configured as a set of modular areas extending parallel to each other, each having a rectangular elongate source area perimetrically surrounded by a narrow gate area. The modular areas are separated from each other by regions with the drain area extending parallel and connected at the opposite ends thereof to a second closed region with the drain area forming a device outer peripheral edge.

Abstract: A laterally diffused metal oxide semiconductor transistor. The laterally diffused metal oxide semiconductor transistor includes a substrate, a drain formed thereon, a source formed on the substrate, comprising a plurality of individual sub-sources respectively corresponding to various sides of the drain, a plurality of channels formed in the substrate between the sub-sources and the drain, a gate overlying a portion of the sub-sources and the channels, and a drift layer formed in the substrate underneath the drain.

Abstract: Embodiments of the invention relate to field effect transistors. The field effect transistor includes a gate electrode for providing a gate field, a first electrode including a conductive material having a low carrier density and a low density of electronic states, a second electrode, and a semiconductor. Contact barrier modulation includes barrier height lowering of a Schottky contact between the first electrode and the semiconductor. In some embodiments of the invention, a vertical field effect transistor employs an electrode comprising a conductive material with a low density of states such that the transistors contact barrier modulation comprises barrier height lowering of the Schottky contact between the electrode with a low density of states and the adjacent semiconductor by a Fermi level shift.

Abstract: A trench semiconductor power device having active cells under gate metal pad to increase total active area for lowering on-resistance is disclosed. The gate metal pad is not only for gate wire bonding but also for active cells disposition. Therefore, the device die can be shrunk so that the number of devices per wafer is increased for die cost reduction. Moreover, the device can be packaged into smaller type package for further cost reduction.

Abstract: A power semiconductor device that includes a buried source electrode disposed at the bottom of a trench below a respective gate electrode, and a source connector including a finger electrically connecting the buried source to the source contact of the device, and a process for fabricating the device.

Abstract: Power MOS device of the type comprising a plurality of elementary power MOS transistors having respective gate structures and comprising a gate oxide with double thickness having a thick central part and lateral portions of reduced thickness. Such device exhibiting gate structures comprising first gate conductive portions overlapped onto said lateral portions of reduced thickness to define, for the elementary MOS transistors, the gate electrodes, as well as a conductive structure or mesh. Such conductive structure comprising a plurality of second conductive portions overlapped onto the thick central part of gate oxide and interconnected to each other and to the first gate conductive portions by means of a plurality of conducive bridges.

Abstract: A MOS transistor having an increased gate-drain capacitance is described. One embodiment provides a drift zone of a first conduction type. At least one transistor cell has a body zone, a source zone separated from the drift zone by the body zone, and a gate electrode, which is arranged adjacent to the body zone and which is dielectrically insulated from the body zone by a gate dielectric. At least one compensation zone of the first conduction type is arranged in the drift zone. At least one feedback electrode is arranged at a distance from the body zone, which is dielectrically insulated from the drift zone by a feedback dielectric and which is electrically conductively connected to the gate electrode.

Abstract: Power MOS device of the type comprising a plurality of elementary power MOS transistors having respective gate structures and comprising a gate oxide with double thickness having a thick central part and lateral portions of reduced thickness. Such device exhibiting gate structures comprising first gate conductive portions overlapped onto said lateral portions of reduced thickness to define, for the elementary MOS transistors, the gate electrodes, as well as a conductive structure or mesh. Such conductive structure comprising a plurality of second conductive portions overlapped onto the thick central part of gate oxide and interconnected to each other and to the first gate conductive portions by means of a plurality of conducive bridges.

Abstract: Provided is a power semiconductor device including a semiconductor substrate, in which a current flows in a thickness direction of the semiconductor substrate. The semiconductor substrate includes a resistance control structure configured so that a resistance to the current becomes higher in a central portion of the semiconductor substrate than a peripheral portion of the semiconductor substrate.

Abstract: A semiconductor memory includes a semiconductor substrate, a buried insulating film formed on a part of an upper surface of the semiconductor substrate, and a semiconductor layer formed on another part of the upper surface of the semiconductor substrate. Each of the memory cell transistors comprises a first-conductivity-type source region, a first-conductivity-type drain region, and a first-conductivity-type channel region arranged in the semiconductor layer in the column direction, and a gate portion formed on a side surface of the channel region in the row direction.

Abstract: Provided is a power semiconductor device including a semiconductor substrate, in which a current flows in a thickness direction of the semiconductor substrate. The semiconductor substrate includes a resistance control structure configured so that a resistance to the current becomes higher in a central portion of the semiconductor substrate than a peripheral portion of the semiconductor substrate.

Abstract: A semiconductor device includes a semiconductor substrate; a well of a first conductivity type in the semiconductor substrate; a first element; and a first vertical transistor. The first element supplies potential to the well, the first element being in the well. The first element may include, but is not limited to, a first pillar body of the first conductivity type. The first pillar body has an upper portion that includes a first diffusion layer of the first conductivity type. The first diffusion layer is greater in impurity concentration than the well. The first vertical transistor is in the well. The first vertical transistor may include a second pillar body of the first conductivity type. The second pillar body has an upper portion that includes a second diffusion layer of a second conductivity type.

Abstract: In a vertical-type semiconductor device, a method of manufacturing the same and a method of operating the same, the vertical-type semiconductor device includes a single-crystalline semiconductor pattern having a pillar shape provided on a substrate, a gate surrounding sidewalls of the single-crystalline semiconductor pattern and having an upper surface lower than an upper surface of the single-crystalline semiconductor pattern, a mask pattern formed on the upper surface of the gate, the mask pattern having an upper surface coplanar with the upper surface of the single-crystalline semiconductor pattern, a first impurity region in the substrate under the single-crystalline semiconductor pattern, and a second impurity region under the upper surface of the single-crystalline semiconductor pattern. The vertical-type pillar transistor formed in the single-crystalline semiconductor pattern may provide excellent electrical properties.

Abstract: Memory devices are described along with methods for manufacturing. A memory device as described herein comprises a plurality of word lines overlying a plurality of bit lines, and a plurality of field effect transistors. Field effect transistors in the plurality of field effect transistors comprises a first terminal electrically coupled to a corresponding bit line in the plurality of bit lines, a second terminal overlying the first terminal, and a channel region separating the first and second terminals and adjacent a corresponding word line in the plurality of word lines. The corresponding word line acts as the gate of the field effect transistor. A dielectric separates the corresponding word line from the channel region. A memory plane comprises programmable resistance memory material electrically coupled to respective second terminals of the field effect transistors, and conductive material on the programmable resistance memory material and coupled to a common voltage.

Abstract: A semiconductor device includes a semiconductor substrate, a first diffusion region, a gate insulating film, a gate electrode, a second diffusion region and a contact plug. The semiconductor substrate includes a base and at least a pillar. The first diffusion region is disposed in the base. The gate insulating film covers a side surface of the pillar. The gate electrode is separated from the pillar by the gate insulating film. The second diffusion region is disposed in an upper portion of the pillar. The contact plug is connected to the second diffusion region. The contact plug is connected to the entirety of the top surface of the pillar.

Abstract: A vertical thin film transistor and a method for manufacturing the same and a display device including the vertical thin film transistor and a method for manufacturing the same are disclosed. The vertical thin film transistor is applied to a substrate. In the present invention, a gate layer of the vertical thin film transistor is formed to have a plurality of concentric annular structures and the adjacent concentric annular structures are linked. By the concentric annular structures of the gate electrode layer, resistance to stress and an on-state current of the vertical thin film transistor can be increased.

Abstract: An integrated circuit device includes a semiconductor body fitted with a first electrode and a second electrode on opposite surfaces. A control electrode on an insulating layer controls channel regions of body zones for a current flow between the two electrodes. A drift section adjoining the channel regions comprises drift zones and charge compensation zones. A part of the charge compensation zones includes conductively connected charge compensation zones electrically connected to the first electrode. Another part includes nearly-floating charge compensation zones, so that an increased control electrode surface has a monolithically integrated additional capacitance CZGD in a cell region of the semiconductor device.

Abstract: MOSFET is provided with SiC film. SiC film has a facet on its surface, and the length of one period of the facet is 100 nm or more, and the facet is used as channel. Further, a manufacturing method of MOSFET includes: a step of forming SiC film; a heat treatment step of heat-treating SiC film in a state where Si is supplied on the surface of SiC film; and a step of forming the facet obtained on the surface of SiC film by the heat treatment step into a channel. Thereby, it is possible to sufficiently improve the characteristics.

Abstract: A semiconductor device as described herein includes a body region of a first conductivity type adjoining a channel region of a second conductivity at a first side of the channel region. A gate control region of the first conductivity type adjoins the channel region at a second side of the channel region opposed to the first side, the channel region being configured to be controlled in its conductivity by voltage application between the gate control region and the body region. A source zone of the second conductivity type is arranged within the body region and a channel stop zone of the second conductivity type is arranged at the first side, the channel stop zone being arranged at least partly within at least one of the body region and the channel region. The channel stop zone includes a maximum concentration of dopants lower than a maximum concentration of dopants of the source zone.

Abstract: A semiconductor device includes: a drift layer having a superjunction structure; a semiconductor base layer selectively formed in a part of one surface of the drift layer; a first RESURF layer formed around a region having the semiconductor base layer formed thereon; a second semiconductor RESURF layer of a conductivity type which is opposite to a conductivity type of the first semiconductor RESURF layer; a first main electrode connected to a first surface of the drift layer; and a second main electrode connected to a second surface of the drift layer. The first RESURF layer is connected to the semiconductor base layer. The second semiconductor RESURF layer is in contact with the first semiconductor RESURF layer.

Abstract: A semiconductor package may comprise a semiconductor substrate, a MOSFET device having a plurality cells formed on the substrate, and a source region common to all cells disposed on a bottom of the substrate. Each cell comprises a drain region on a top of the semiconductor device, a gate to control a flow of electrical current between the source and drain regions, a source contact proximate the gate; and an electrical connection between the source contact and source region. At least one drain connection is electrically coupled to the drain region. Source, drain and gate pads are electrically connected to the source region, drain region and gates of the devices. The drain, source and gate pads are formed on one surface of the semiconductor package. The cells are distributed across the substrate, whereby the electrical connections between the source contact of each device and the source region are distributed across the substrate.

Abstract: A silicon carbide semiconductor device having excellent performance characteristics and a method of manufacturing the same are obtained. An extended terrace surface is formed at a surface of an initial growth layer on a 4H—SiC substrate by annealing with the initial growth layer covered with an Si film, and then a new growth layer is epitaxially grown on the initial growth layer. A 3C—SiC portion having a polytype stable at a low temperature is grown on the extended terrace surface, and a 4H—SiC portion is grown on the other region. A trench is formed by selectively removing the 3C—SiC portion with the 4H—SiC portion remaining, and a gate electrode of a UMOSFET is formed in the trench. A channel region of the UMOSFET can be controlled to have a low-order surface, and a silicon carbide semiconductor device having high channel mobility and excellent performance characteristics is obtained.

Abstract: The trench type semiconductor device includes a gate insulating film placed on the bottom surface and the sidewall surface of the trench formed from the surface of a first base layer; a gate electrode placed on the gate insulating film and fills up into a trench; an interlayer insulating film covering the gate electrode; a second base layer placed on the surface of the first base layer, and is formed more shallowly than the bottom surface of the trench; a source layer placed on the surface of the second base layer; a source electrode connected to the second base layer in the bottom surface of a self-aligned contact trench formed in the second base layer by applying the interlayer insulating film as a mask, and is connected to the source layer in the sidewall surface; a drain layer placed at the back side of the first base layer; and a drain electrode placed at the drain layer, for achieving the minute structure by the self-alignment, reducing the on resistance, and improving the breakdown capability, and prov

Abstract: An integrated circuit (200) includes one of more transistors (210) on or in a substrate (10) having semiconductor surface layer, the surface layer having a top surface. At least one of the transistors are drain extended metal-oxide-semiconductor (DEMOS) transistor (210). The DEMOS transistor includes a drift region (14) in the surface layer having a first dopant type, a field dielectric (23) in or on a portion of the surface layer, and a body region of a second dopant type (16) within the drift region (14). The body region (16) has a body wall extending from the top surface of the surface layer downwards along at least a portion of a dielectric wall of an adjacent field dielectric region. A gate dielectric (21) is on at least a portion of the body wall. An electrically conductive gate electrode (22) is on the gate dielectric (21) on the body wall.

Abstract: In one aspect, a lateral MOS device is provided. The lateral MOS device includes a gate electrode disposed at least partially in a gate trench to apply a voltage to a channel region, and a drain electrode spaced from the gate electrode, and in electrical communication with a drift region having a boundary with a lower end of the channel region. The device includes a gate dielectric layer in contact with the gate electrode, and disposed between the gate electrode and the drain electrode. The channel region is adjacent to a substantially vertical wall of the gate trench. The device includes a field plate contacting the gate electrode and configured to increase a breakdown voltage of the device.

Abstract: A semiconductor device formed on a semiconductor substrate may include a component formed in a contact trench located in an active cell region. The component may comprise a barrier metal deposited on a bottom and portions of sidewalls of the contact trench and a tungsten plug deposited in a remaining portion of the contact trench. The barrier metal may comprise first and second metal layers. The first metal layer may be proximate to the sidewall and the bottom of the contact trench. The first metal layer may include a nitride. The second metal layer may be between the first metal layer and the tungsten plug and between the tungsten plug and the sidewall. The second metal layer covers portions of the sidewalls of not covered by the first metal layer.

Abstract: A field effect transistor, in accordance with one embodiment, includes a metal-oxide-semiconductor field effect transistor (MOSFET) having a junction field effect transistor (JFET) embedded as a body diode.

Abstract: A method of making nanostructures using a self-assembled monolayer of organic spheres is disclosed. The nanostructures include bowl-shaped structures and patterned elongated nanostructures. A bowl-shaped nanostructure with a nanorod grown from a conductive substrate through the bowl-shaped nanostructure may be configured as a field emitter or a vertical field effect transistor. A method of separating nanoparticles of a desired size employs an array of bowl-shaped structures.

Abstract: A vertical transistor and a method for forming the same. The vertical transistor includes a semiconductor substrate having pillar type active patterns formed on a surface thereof; first junction regions formed in the surface of the semiconductor substrate on both sides of the active patterns; screening layers formed on sidewalls of the first junction regions; second junction regions formed on upper surfaces of the active patterns; and gates formed on sidewalls of the active patterns including the second junction regions to overlap with at least portions of the first junction regions.

Abstract: A semiconductor device including a semiconductor section including a semiconductor element and a recess formed in one of main surfaces and a metallic member at least a part of which is embedded in the recess. A void is formed in a region of the metallic member corresponding to the recess.

Abstract: According to an exemplary embodiment, a method for fabricating a MOS transistor, such as an LDMOS transistor, includes forming a gate stack over a well. The method further includes forming a recess in the well adjacent to a first sidewall of the gate stack. The method further includes forming a source region in the recess such that a heterojunction is formed between the source region and the well. The method further includes forming a drain region spaced apart from a second sidewall of the gate stack. In one embodiment, the source region can comprise silicon germanium and the well can comprise silicon. In another embodiment, the source region can comprise silicon carbide and the well can comprise silicon.

Abstract: There is provided a semiconductor device formed of a highly integrated high-speed CMOS inverter coupling circuit using SGTs provided on at least two stages. A semiconductor device according to the present invention is formed of a CMOS inverter coupling circuit in which n (n is two or above) CMOS inverters are coupled with each other, each of the n inverters has: a pMOS SGT; an nMOS SGT, an input terminal arranged so as to connect a gate of the pMOS SGT with a gate of the nMOS SGT; an output terminal arranged to connect a drain diffusion layer of the pMOS SGT with a drain diffusion layer of the nMOS SGT in an island-shaped semiconductor lower layer; a pMOS SGT power supply wiring line arranged on a source diffusion layer of the pMOS SGT; and an nMOS SGT power supply wiring line arranged on a source diffusion layer of the NMOS SGT, and an n?1th output terminal is connected with an nth input terminal.

Abstract: A trenched semiconductor power device includes a trenched gate insulated by a gate insulation layer and surrounded by a source region encompassed in a body region above a drain region disposed on a bottom surface of a semiconductor substrate. The source region surrounding the trenched gate includes a metal of low barrier height to function as a Schottky source. The metal of low barrier height further may include a PtSi or ErSi layer. In a preferred embodiment, the metal of low barrier height further includes an ErSi layer. The metal of low barrier height further may be a metal silicide layer having the low barrier height. A top oxide layer is disposed under a silicon nitride spacer on top of the trenched gate for insulating the trenched gate from the source region. A source contact disposed in a trench opened into the body region for contacting a body-contact dopant region and covering with a conductive metal layer such as a Ti/TiN layer.

Abstract: The invention relates to a metallization for an IGBT or a diode. In the case of this metallization, a copper layer (10, 12) having a layer thickness of approximately 50 ?m is applied to the front side and/or rear side of a semiconductor body (1) directly or if need be via a diffusion barrier layer (13, 14). The layer (8, 12) has a specific heat capacity that is at least a factor of 2 higher than the specific heat capacity of the semiconductor body (1). It simultaneously serves for producing a field stop layer (5) by proton implantation through the layer (12) from the rear side and for masking a proton or helium implantation for the purpose of charge carrier lifetime reduction from the front side of the chip (1).

Abstract: In a semiconductor device and associated methods, the semiconductor device includes a substrate, an insulation layer on the substrate, a conductive structure on the insulation layer, the conductive structure including at least one metal silicide film pattern, a semiconductor pattern on the conductive structure, the semiconductor pattern protruding upwardly from the conductive structure, a gate electrode at least partially enclosing the semiconductor pattern, the gate electrode being spaced apart from the conductive structure, a first impurity region at a lower portion of the semiconductor pattern, and a second impurity region at an upper portion of the semiconductor pattern.

Abstract: Manufacturing a power transistor by forming a gate structure on a first layer, forming a trench in the first layer, self aligned with the gate structure, and forming part of the transistor in the trench. By forming a spacer next to the gate, the spacer and gate can be used as a mask when forming the trench, to allow space for a source region next to the gate. The self-aligning rather than forming the gate after the trench means the alignment is more accurate, allowing size reduction. Another aspect involves forming a trench in a first layer, filling the trench, forming a second layer on either side of the trench with lateral overgrowth over the trench, and forming a source region in the second layer to overlap the trench. This overlap can enable the chip area to be reduced.