Abstract: A static random access memory fabrication array includes at least one p-type field effect transistor, including a gate stack and isolating spacers forming a gate having a gate length Lgate and an effective gate length, Leff and a source and drain region adjacent the gate stack, wherein the source and drain regions are formed from a low extension dose implant that decreases a difference between Lgate and Leff.

Abstract: According to one embodiment, a first distance is a distance between both ends of the first insulating film in a direction connecting the fourth semiconductor layer and the sixth semiconductor layer. The first distance in the first region is longer than the first distance in the second region. A second distance is a distance between an edge of the second insulating film on an inner peripheral side of the second semiconductor layer and an edge of the third semiconductor layer on an outer peripheral side of the second semiconductor layer. The second distance in the first region is shorter than the second distance in the second region.

Abstract: Embodiments of laterally diffused metal oxide semiconductor (LDMOS) transistors are provided. An LDMOS transistor includes a substrate having a source region, channel region, and a drain region. A first implant is formed to a first depth in the substrate. A gate electrode is formed over the channel region in the substrate between the source region and the drain region. A second implant is formed in the source region of the substrate; the second implant is laterally diffused under the gate electrode a predetermined distance. A third implant is formed to a second depth in the drain region of the substrate; the second depth is less than the first depth.

Abstract: A method of fabricating asymmetrical spacers, structures fabricated using asymmetrical spacers and an apparatus for fabricating asymmetrical spacers. The method includes: forming on a substrate, a structure having a top surface and opposite first and second sidewalls and having a longitudinal axis parallel to the sidewalls; forming a conformal layer on the top surface of the substrate, the top surface of the structure and the sidewalls of the structure; tilting the substrate about a longitudinal axis relative to a flux of reactive ions, the flux of reactive ions striking the conformal layer at acute angle; and exposing the conformal layer to the flux of reactive ions until the conformal layer is removed from the top surface of the structure and the top surface of the substrate leaving a first spacer on the first sidewall and a second spacer on the second sidewall, the first spacer thinner than the second spacer.

Abstract: An integrated circuit is formed on a semiconductor substrate and includes a trench conductor and a first transistor formed on the surface of the substrate. The transistor includes: a transistor gate structure, a first doped region extending in the substrate between a first edge of the gate structure and an upper edge of the trench conductor, and a first spacer formed on the first edge of the gate structure and above the first doped region. The first spacer completely covers the first doped region and a silicide is present on the trench conductor but is not present on the surface of the first doped region.

Abstract: A non-volatile memory cell includes a p-channel non-volatile transistor having a source and a drain defining a channel and a gate overlying the channel and an n-channel non-volatile transistor having a source and a drain defining a channel and a gate overlying the channel. In at least one of the p-channel non-volatile transistor and the n-channel non-volatile transistor, a lightly-doped drain region extends from the drain into the channel.

Abstract: A device includes a semiconductor region in a semiconductor chip, a gate dielectric layer over the semiconductor region, and a gate electrode over the gate dielectric. A drain region is disposed at a top surface of the semiconductor region and adjacent to the gate electrode. A gate spacer is on a sidewall of the gate electrode. A dielectric layer is disposed over the gate electrode and the gate spacer. A conductive field plate is over the dielectric layer, wherein the conductive field plate has a portion on a drain side of the gate electrode. A deep metal via is disposed in the semiconductor region. A source electrode is underlying the semiconductor region, wherein the source electrode is electrically shorted to the conductive field plate through the deep metal via.

Abstract: A static random access memory fabrication method includes forming a gate stack on a substrate, forming isolating spacers adjacent the gate stack, the isolating spacers and gate stack having a gate length, forming a source and drain region adjacent the gate stack, which generates an effective gate length, wherein the source and drain regions are formed from a low extension dose implant that varies a difference between the gate length and the effective gate length.

Abstract: Semiconductor layers on active areas for transistors in a memory cell region (region A) and a peripheral circuit region (region B) are simultaneously epitaxially grown in the same thickness in which the adjacent semiconductor layers in region A do not come into contact with each other. Only semiconductor layer (10) in region B is also grown from the surface of a substrate which is exposed when only the surface of STI (2) in region B is drawn back, so that a facet (F) of the semiconductor layer 10 is formed outside the active area, followed by ion-implantation to form a high density diffusion layer (11) in region B. Accordingly, short circuit between semiconductor layers on source/drain electrodes of transistors in region A is prevented, and uniformity of the junction depth of the layer (11) of the source/drain electrodes including an ESD region in a transistor of region B is obtained, thereby restricting the short channel effect.

Abstract: A high voltage transistor structure comprises a first double diffused region and a second double diffused region formed in a first well of a substrate, wherein the first and second double diffused regions are of the same conductivity as the substrate, a first drain/source region formed in the first double diffused region, a first gate electrode formed over the first well and a second drain/source region formed in the second double diffused region. The high voltage transistor structure further comprises a first spacer formed on a first side of the first gate electrode, wherein the first spacer is between the first drain/source region and the first gate electrode, a second spacer formed on a second side of the first gate electrode and a first oxide protection layer formed between the second drain/source region and the second spacer.

Abstract: LDD regions are provided with high implant energy in devices with reduced thickness poly-silicon layers and source/drain junctions. Embodiments include forming an oxide layer on a substrate surface, forming a poly-silicon layer over the oxide layer, forming first and second trenches through the oxide and poly-silicon layers and below the substrate surface, defining a gate region therebetween, implanting a dopant in a LDD region through the first and second trenches, forming spacers on opposite side surfaces of the gate region and extending into the first and second trenches, and implanting a dopant in a source/drain region below each of the first and second trenches.

Abstract: Disclosed is a semiconductor component, including: a drift zone arranged between a first and a second connection zone; a channel control layer of an amorphous semi-insulating material arranged adjacent to the drift zone.

Abstract: Disclosed are example bipolar transistors capable of reducing the area of a collector, reducing the distance between a base and a collector, and/or reducing the number of ion implantation processes. A bipolar transistor may includes a trench formed by etching a portion of a semiconductor substrate. A first collector may be formed on the inner wall of the trench. A second collector may be formed inside the semiconductor substrate in the inner wall of the trench. A first isolation film may be formed on the sidewall of the first collector. An intrinsic base may be connected to the third collector. An extrinsic base may be formed on the intrinsic base and inside the first isolation film. A second isolation film may be formed on the inner wall of the extrinsic base. An emitter may be formed by burying a conductive material inside the second isolation film.

Abstract: Some aspects relate to a semiconductor device disposed on a semiconductor substrate. The device includes an STI region that laterally surrounds a base portion of a semiconductor fin. An anode region, which has a first conductivity type, and a cathode region, which has a second conductivity type, are arranged in an upper portion of the semiconductor fin. A first doped base region, which has the second conductivity type, is arranged in the base of the fin underneath the anode region. A second doped base region, which has the first conductivity type, is arranged in the base of the fin underneath the cathode region. A current control unit is arranged between the anode region and the cathode region. The current control unit is arranged to selectively enable and disable current flow in the upper portion of the fin based on a trigger signal. Other devices and methods are also disclosed.

Abstract: A method is provided for fabricating an MOS transistor. The method includes providing a semiconductor substrate, and forming a gate structure having a gate dielectric layer and a gate metal layer on the semiconductor substrate. The method also includes forming offset sidewall spacers at both sides of the gate structure, and forming lightly doped regions in semiconductor substrate at both sides of the gate structure. Further, the method includes forming a first metal silicide region in each of the lightly doped regions, and forming main sidewall spacers at both sides of the gate structure. Further, the method includes forming heavily doped regions in semiconductor substrate at both sides of the gate structure and the main sidewall spacers, and forming a second metal silicide region in each of the heavily doped regions.

Abstract: A semiconductor device includes a first well and a second well implanted in a semiconductor substrate. The semiconductor device further includes a gate structure above the first and second wells between a raised source structure and a raised drain structure. The raised source structure above is in contact with the first well and connected with the gate structure through a first semiconductor fin structure. The raised drain structure above and in contact with the second well and connected with a second semiconductor fin structure. The second semiconductor fin structure includes at least a gap and a lightly doped portion.

Abstract: A semiconductor device includes a gate pattern over source and drain regions. The gate pattern includes a first gate adjacent the source region and a second gate adjacent the drain region. A concentration of dopants in the first gate is higher than a concentration of dopants in the second gate. As a result, channels are produced between the source and drain regions based on different threshold voltages.

Abstract: An advanced transistor with punch through suppression includes a gate with length Lg, a well doped to have a first concentration of a dopant, and a screening region positioned under the gate and having a second concentration of dopant. The second concentration of dopant may be greater than 5×1018 dopant atoms per cm3. At least one punch through suppression region is disposed under the gate between the screening region and the well. The punch through suppression region has a third concentration of a dopant intermediate between the first concentration and the second concentration of dopant. A bias voltage may be applied to the well region to adjust a threshold voltage of the transistor.

Abstract: A lateral diffused metal oxide semiconductor (LDMOS) transistor is provided. The LDMOS transistor includes a substrate having a source region, channel region, and a drain region. A first implant is formed to a first depth in the substrate. A gate electrode is formed over the channel region in the substrate between the source region and the drain region. A second implant is formed in the source region of the substrate; the second implant is laterally diffused under the gate electrode a predetermined distance. A third implant is formed to a second depth in the drain region of the substrate; the second depth is less than the first depth. A method for forming the LDMOS transistor is also provided.

Abstract: Various embodiments of a power MOS device structure are disclosed. In one aspect, a power MOS device structure includes a plurality of LDMOS and a plurality of bonding pads. The basic units of LDMOS are coupled in parallel and electrically coupled to the bonding pads to couple to a gate terminal, a source terminal, a drain terminal and a substrate of each of the basic units of LDMOS. The basic units of LDMOS are disposed below the bonding pads. The bonding pads include a single layer of metal with a thickness of 3.5 um to 4.5 um and a width of 1.5 um to 2.5 um. The region below the bonding pads of the power MOS device of the present disclosure is utilized to increase the number of basic units of LDMOS, thereby effectively reducing the on-resistance.

Abstract: According to an exemplary embodiment, a method for fabricating a MOS transistor, such as an LDMOS transistor, includes forming a self-aligned lightly doped region in a first well underlying a first sidewall of a gate. The method further includes forming a self-aligned extension region under a second sidewall of the gate, where the self-aligned extension region extends into the first well from a second well. The method further includes forming a drain region spaced apart from the second sidewall of the gate. The method further includes forming a source region in the self-aligned lightly doped region and the first well. The self-aligned lightly doped region and the self-aligned extension region define a channel length of the MOS transistor, such as an LDMOS transistor.

Abstract: A semiconductor device is provided, in which work of a parasitic bipolar transistor can be suppressed and a potential difference can be provided between a source region and a back gate region. A high voltage tolerant transistor formed over a semiconductor substrate includes: a well region of a first conductivity type; a first impurity region as the source region; and a second impurity region as a drain region. The semiconductor device further includes a third impurity region and a gate electrode for isolation. The third impurity region is formed, in planar view, between a pair of the first impurity regions, and from which a potential of the well region is extracted. The gate electrode for isolation is formed over the main surface between the first impurity region and the third impurity region.

Abstract: A transistor structure that improves ESD withstand voltages is offered. A high impurity concentration drain layer is formed in a surface of an intermediate impurity concentration drain layer at a location separated from a drain-side end of a gate electrode. And a P-type impurity layer is formed in a surface of a substrate between the gate electrode and the high impurity concentration drain layer so as to surround the high impurity concentration drain layer. When a parasitic bipolar transistor is turned on by an abnormal surge, electrons travel from a source electrode to a drain electrode. Here, electrons travel dispersed in the manner to avoid a vicinity X of the surface of the substrate and travel through a deeper path to the drain electrode as indicated by arrows in FIG. 4.

Abstract: A semiconductor structure, which serves as the core of a semiconductor fabrication platform, has a combination of empty-well regions and filled-well regions variously used by electronic elements, particularly insulated-gate field-effect transistors (“IGFETs”), to achieve desired electronic characteristics. A relatively small amount of semiconductor well dopant is near the top of an empty well. A considerable amount of semiconductor well dopant is near the top of a filled well. Some IGFETs (100, 102, 112, 114, 124, and 126) utilize empty wells (180, 182, 192, 194, 204, and 206) in achieving desired transistor characteristics. Other IGFETs (108, 110, 116, 118, 120, and 122) utilize filled wells (188, 190, 196, 198, 200, and 202) in achieving desired transistor characteristics.

Abstract: Semiconductor devices including a stressor in a recess and methods of forming the semiconductor devices are provided. The methods may include forming a trench in an active region and the trench may include a notched portion of the active region. The methods may also include forming an embedded stressor in the trench. The embedded stressor may include a lower semiconductor layer and an upper semiconductor layer, which has a width narrower than a width of the lower semiconductor layer. A side of the upper semiconductor layer may not be aligned with a side of the lower semiconductor layer and an uppermost surface of the upper semiconductor layer may be higher than an uppermost surface of the active region.

Abstract: The present invention discloses a double diffused metal oxide semiconductor (DMOS) device and a manufacturing method thereof. The DMOS device includes: an isolation structure for defining device regions; a gate with a ring-shaped structure; a drain located outside the ring; and a lightly doped drain, a source, and a body electrode located inside the ring. To increase the sub-threshold voltage at the corners of the gate, the corners are located completely on the isolation structure, or the lightly doped drain is apart from the corners by a predetermined distance.

Abstract: A semiconductor structure comprising a semiconductor unit, a first conductive structure, a first conductive plug, and a second conductive structure is provided. The semiconductor unit has a substrate on a first side of the semiconductor unit. The substrate has at least a hole. The first conductive plug is in the hole and the hole may be full of the conductive plug. The first conductive structure is on the surface of the semiconductor unit. The surface is at the first side of the semiconductor unit. The second conductive structure is on a surface at a second side of the substrate of the semiconductor unit.

Abstract: The present invention discloses a double diffused metal oxide semiconductor (DMOS) device and a manufacturing method thereof. The DMOS device includes: an isolation structure for defining device regions; a gate with a ring-shaped structure; a drain located outside the ring; and a lightly doped drain, a source, and a body electrode located inside the ring. To increase the sub-threshold voltage at the corners of the gate, the corners are located completely on the isolation structure, or the lightly doped drain is apart from the corners by a predetermined distance.

Abstract: A radio frequency (RF) laterally diffused metal oxide semiconductor (LDMOS) device is disclosed which additionally includes a lightly-doped P-type buried layer under a P-type channel region and a moderately-dope P-type buried layer in the lightly-doped P-type buried layer. The two buried layers result in a lower base resistance for an equivalent parasitic NPN transistor, thereby impeding the occurrence of snapback in the device. Additionally, an equivalent reverse-biased diode formed between the channel region and the buried layers is capable of clamping the drain-source voltage of the device and sinking redundant currents to a substrate thereof. Furthermore, the design of a gate oxide layer of the RF LDMOS device to have a greater thickness at a proximal end to a drain region can help to reduce the hot-carrier effect, and having a smaller thickness at a proximal end to the source region can improve the transconductance of the RF LDMOS device.

Abstract: The present invention discloses a double diffused metal oxide semiconductor (DMOS) device and a manufacturing method thereof. The DMOS device includes: an isolation structure for defining device regions; a gate with a ring-shaped structure; a drain located outside the ring; and a lightly doped drain, a source, and a body electrode located inside the ring. To increase the sub-threshold voltage at the corners of the gate, the corners are located completely on the isolation structure, or the lightly doped drain is apart from the corners by a predetermined distance.

Abstract: A method of forming a hybrid semiconductor structure on an SOI substrate. The method includes an integrated process flow to form a nanowire mesh device and a PDSOI device on the same SOI substrate. Also included is a semiconductor structure which includes the nanowire mesh device and the PDSOI device on the same SOI substrate.

Abstract: The present invention discloses a double diffused metal oxide semiconductor (DMOS) device and a manufacturing method thereof. The DMOS device includes: an isolation structure for defining device regions; a gate with a ring-shaped structure; a drain located outside the ring; and a lightly doped drain, a source, and a body electrode located inside the ring. To increase the sub-threshold voltage at the corners of the gate, the corners are located completely on the isolation structure, or the lightly doped drain is apart from the corners by a predetermined distance.

Abstract: A DMOS transistor is fabricated with its source/body/deep body regions formed on the walls of a first set of trenches, and its drain regions formed on the walls of a different set of trenches. A gate region that is formed in a yet another set of trenches can be biased to allow carriers to flow from the source to the drain. Lateral current low from source/body regions on trench walls increases the active channel perimeter to a value well above the amount that would be present if the device was fabricated on just the surface of the wafer. Masking is avoided while open trenches are present. A transistor with a very low on-resistance per unit area is obtained.

Abstract: A LDMOS transistor is implemented in a first impurity region on a substrate. The LDMOS transistor has a source that includes a second impurity region. The second impurity region is implanted into the surface of the substrate within the first impurity region. Additionally, the LDMOS transistor has a drain that includes a third impurity region. The third impurity region is implanted into the surface of the substrate within the first impurity region. The third impurity region is spaced a predetermined distance away from a gate of the LDMOS transistor. The drain of the LDMOS transistor further includes a fourth impurity region within the third impurity region. The fourth impurity region provides an ohmic contact for the drain.

Abstract: A method of forming a semiconductor device is provided. The method includes preparing a substrate having a transistor region and an alignment region, forming a first trench and a second trench in the substrate of the transistor region and in the substrate of the alignment region, respectively, forming a drift region in the substrate of the transistor region, forming two third trenches respectively adjacent to two ends of the drift region, and forming an isolation pattern in the first trench, a buried dielectric pattern in the second trench, and dielectric patterns in the two third trenches, respectively. A depth of the first trench is less than a depth of the third trenches, and the depth of the first trench is equal or substantially equal to a depth of the second trench.

Abstract: A laterally diffused metal-oxide-semiconductor transistor device includes a substrate having a first conductivity type with a semiconductor layer formed over the substrate. A source region and a drain extension region of the first conductivity type are formed in the semiconductor layer. A body region of a second conductivity type is formed in the semiconductor layer. A conductive gate is formed over a gate dielectric layer that is formed over a channel region. A drain contact electrically connects the drain extension region to the substrate and is laterally spaced from the channel region. The drain contact includes a highly-doped drain contact region formed between the substrate and the drain extension region in the semiconductor layer, wherein a topmost portion of the highly-doped drain contact region is spaced from the upper surface of the semiconductor layer. A source contact electrically connects the source region to the body region.

Abstract: A semiconductor device is provided. The semiconductor device includes a gate on a substrate, a source region at a first side of the gate, a first conductive type body region under the source region, a second conductive type drain region at a second side of the gate, a device isolation region in the substrate between the source region and the drain region and overlapping part of the gate, and a first buried layer extending in a direction from the source region to the drain region, the first buried layer under the body region, overlapping part of the device isolation region, and not overlapping the drain region.

Abstract: The present invention discloses a double diffused metal oxide semiconductor (DMOS) device and a manufacturing method thereof. The DMOS device is formed in a first conductive type substrate, and includes a second conductive type high voltage well, a field oxide region, a gate, a second conductive type source, a second conductive type drain, a first conductive type body region, and a first conductive type deep well. The deep well is formed beneath and adjacent to the high voltage well in a vertical direction. The deep well and the high voltage well are defined by a same lithography process step.

Abstract: A semiconductor device includes: a p-type active region; a gate electrode traversing the active region; an n-type LDD region having a first impurity concentration and formed from a drain side region to a region under the gate electrode; a p-type channel region having a second impurity concentration and formed from a source side region to a region under the gate electrode to form an overlap region with the LDD region under the gate electrode, the channel region being shallower than the LDD region; an n-type source region formed outside the gate electrode; and an n+-type drain region having a third impurity concentration higher than the first impurity concentration formed outside and spaced from the gate electrode, wherein an n-type effective impurity concentration of an intermediate region between the gate electrode and the n+-type drain region is higher than an n-type effective impurity concentration of the overlap region.

Abstract: A transistor and method of making same include a substrate, a conductive gate over the substrate and a channel region in the substrate under the conductive gate. First and second insulating spacers are laterally adjacent to first and second sides of the conductive gate. A source region in the substrate is adjacent to but laterally spaced from the first side of the conductive gate and the first spacer, and a drain region in the substrate is adjacent to but laterally spaced apart from the second side of the conductive gate and the second spacer. First and second LD regions are in the substrate and laterally extend between the channel region and the source or drain regions respectively, each with a portion thereof not disposed under the first and second spacers nor under the conductive gate, and each with a dopant concentration less than that of the source or drain regions.

Abstract: The present disclosure provides a semiconductor device. The semiconductor device includes: a drift region having a first doping polarity formed in a substrate; a doped extension region formed in the drift region and having a second doping polarity opposite the first doping polarity, the doped extension region including a laterally-extending component; a dielectric structure formed over the drift region, the dielectric structure being separated from the doped extension region by a portion of the drift region; a gate structure formed over a portion of the dielectric structure and a portion of the doped extension region; and a doped isolation region having the second doping polarity, the doped isolation region at least partially surrounding the drift region and the doped extension region.

Abstract: Apparatus for semiconductor device structures and related fabrication methods are provided. One method for fabricating a semiconductor device structure involves forming a gate structure overlying a region of semiconductor material, wherein the width of the gate structure is aligned with a <100> crystal direction of the semiconductor material. The method continues by forming recesses about the gate structure and forming a stress-inducing semiconductor material in the recesses.

Abstract: A lateral device includes a gate region connected to a drain region by a drift layer. An insulation region adjoins the drift layer between the gate region and the drain region. Permanent charges are embedded in the insulation region, sufficient to cause inversion in the insulation region.

Abstract: A semiconductor device including a gate electrode formed over a first region of a semiconductor substrate of a first conduction type; a source region and a drain region of the first conduction type formed on both sides of the gate electrode; a channel dope layer of a second conduction type formed in at least a region on a side of the source region of a channel region, the channel dope layer having a concentration gradient of a concentration of a dopant impurity of the second conduction type, which decrease toward the drain region; a first well of the second conduction type having a concentration gradient of a concentration of a dopant impurity of the second conduction type, which decrease toward the drain region; and a second well of the second conduction type formed in the first region, connected to the first well and positioned below the first well.

Abstract: In one embodiment, the semiconductor device includes a first source of a first doping type disposed in a substrate. A first drain of the first doping type is disposed in the substrate. A first gate region is disposed between the first source and the first drain. A first channel region of a second doping type is disposed under the first gate region. The second doping type is opposite to the first doping type. A first extension region of the first doping type is disposed between the first gate and the first drain. The first extension region is part of a first fin disposed in or over the substrate. A first isolation region is disposed between the first extension region and the first drain. A first well region of the first doping type is disposed under the first isolation region. The first well region electrically couples the first extension region with the first drain.

Abstract: A device includes a semiconductor substrate, a drift region in the semiconductor substrate and having a first conductivity type, an isolation region within the drift region, and around which charge carriers drift on a path through the drift region during operation, and a protection region adjacent the isolation region in the semiconductor substrate, having a second conductivity type, and disposed along a surface of the semiconductor substrate.

Abstract: The present disclosure provides a semiconductor device. The semiconductor device includes: a drift region having a first doping polarity formed in a substrate; a doped extension region formed in the drift region and having a second doping polarity opposite the first doping polarity, the doped extension region including a laterally-extending component; a dielectric structure formed over the drift region, the dielectric structure being separated from the doped extension region by a portion of the drift region; a gate structure formed over a portion of the dielectric structure and a portion of the doped extension region; and a doped isolation region having the second doping polarity, the doped isolation region at least partially surrounding the drift region and the doped extension region.

Abstract: A semiconductor structure includes a substrate having a first conductive type, a well having a second conductive type formed in the substrate, a first doped region and a second doped region formed in the well, a field oxide, a first dielectric layer and a second dielectric layer. The field oxide is formed on a surface region of the well and between the first doped region and the second doped region. The first dielectric layer is formed on the surface region of the well and covers an edge portion of the field oxide. The first dielectric layer has a first thickness. The second dielectric layer is formed on the surface region of the well. The second dielectric layer has a second thickness smaller than the first thickness.

Abstract: According to an exemplary embodiment, a method for fabricating a MOS transistor, such as an LDMOS transistor, includes forming a self-aligned lightly doped region in a first well underlying a first sidewall of a gate. The method further includes forming a self-aligned extension region under a second sidewall of the gate, where the self-aligned extension region extends into the first well from a second well. The method further includes forming a drain region spaced apart from the second sidewall of the gate. The method further includes forming a source region in the self-aligned lightly doped region and the first well. The self-aligned lightly doped region and the self-aligned extension region define a channel length of the MOS transistor, such as an LDMOS transistor.

Abstract: LDD regions are provided with high implant energy in devices with reduced thickness poly-silicon layers and source/drain junctions. Embodiments include forming an oxide layer on a substrate surface, forming a poly-silicon layer over the oxide layer, forming first and second trenches through the oxide and poly-silicon layers and below the substrate surface, defining a gate region therebetween, implanting a dopant in a LDD region through the first and second trenches, forming spacers on opposite side surfaces of the gate region and extending into the first and second trenches, and implanting a dopant in a source/drain region below each of the first and second trenches.