Abstract: Semiconductor devices and fabrication methods are provided, in which metal transistor gates are provided for MOS transistors. Metal nitride is formed above a gate dielectric. A lanthaide series metal is implanted into the metal screen layer above the gate dielectric. The lanthaide metal is contained in the screen layer or at the interface between the screen metal layer and the gate dielectric. This process provides adjustment of the gate electrode work function, thereby tuning the threshold voltage of the resulting PMOS or NMOS transistors.

Abstract: Different portions of a continuous loop of semiconductor material are electrically isolated from one another. In some embodiments, the end of the loop is electrically isolated from mid-portions of the loop. In some embodiments, loops of semiconductor material, having two legs connected together at their ends, are formed by a pitch multiplication process in which loops of spacers are formed on sidewalls of mandrels. The mandrels are removed and a block of masking material is overlaid on at least one end of the spacer loops. In some embodiments, the blocks of masking material overlay each end of the spacer loops. The pattern defined by the spacers and the blocks are transferred to a layer of semiconductor material. The blocks electrically connect together all the loops. A select gate is formed along each leg of the loops. The blocks serve as sources/drains.

Abstract: A method is provided of making a gated semiconductor device. Such method can include patterning a single-crystal semiconductor region of a substrate to extend in a lateral direction parallel to a major surface of a substrate and to extend in a direction at least substantially vertical and at least substantially perpendicular to the major surface, the semiconductor region having a first side and a second side opposite, e.g., remote from the first side. A first gate may be formed overlying the first side, the first gate having a first gate length in the lateral direction. A second gate may be formed overlying the second side, the second gate having a second gate length in the lateral direction which is different from the first gate length. In one embodiment, the second gate length may be shorter than the first gate length. In one embodiment, the first gate may consist essentially of polycrystalline silicon germanium and the second gate may consist essentially of polysilicon.

Abstract: Disclosed are embodiments of a semiconductor structure with fins that are positioned on the same planar surface of a wafer and that have channel regions with different heights. In one embodiment the different channel region heights are accomplished by varying the overall heights of the different fins. In another embodiment the different channel region heights are accomplished by varying, not the overall heights of the different fins, but rather by varying the heights of a semiconductor layer within each of the fins. The disclosed semiconductor structure embodiments allow different multi-gate non-planar FETs (i.e., tri-gate or dual-gate FETs) with different effective channel widths to be formed of the same wafer and, thus, allows the beta ratio in devices that incorporate multiple FETs (e.g., static random access memory (SRAM) cells) to be selectively adjusted.

Abstract: A semiconductor device includes: a first group-III nitride semiconductor layer formed on a substrate; a second group-III nitride semiconductor layer made of a single layer or two or more layers, formed on the first group-III nitride semiconductor layer, and acting as a barrier layer; a source electrode, a drain electrode, and a gate electrode formed on the second group-III nitride semiconductor layer, the gate electrode controlling a current flowing between the source and drain electrodes; and a heat radiation film with high thermal conductivity which covers, as a surface passivation film, the entire surface other than a bonding pad.

Abstract: This invention proposes a method for making very low threshold voltage (Vt) metal-gate/high-? CMOSFETs using novel self-aligned low-temperature ultra shallow junctions with gate-first process compatible with VLSI. At 1.2 nm equivalent-oxide thickness (EOT), good effective work-function of 5.3 and 4.1 eV, low Vt of +0.05 and 0.03 V, high mobility of 90 and 243 cm2/Vs, and small 85° C. bias-temperature-instability <32 mV (10 MV/cm, 1 hr) are measured for p- and n-MOS.

Abstract: Methods include making a FinFET device structure having multiple FinFET devices (e.g. ntype and/or ptype) with different metal conductors and/or different high-k insulators in the gates formed on a SOI substrate. One such method includes removing a second semiconductor layer from a second metal layer in a region above a second cap layer, from adjoining regions and from regions adjacent to a second fin.

Abstract: A semiconductor device includes a pair of select gate structures which are opposed to each other and which are formed in a select transistor formation area, each of the select gate structures including a gate insulating film formed on a semiconductor substrate and a gate electrode formed on the gate insulating film, and a pair of memory cell gate structure groups which are formed in a pair of memory cell formation areas between which the select transistor formation area is interposed and each of which has a plurality of memory cell gate structures arranged at the same pitch, the pair of select gate structures having sides which are opposed to each other, and at least the upper portion of each of the opposed sides of the select gate structures being inclined.

Abstract: The present invention relates to a semiconductor device including a Fin type field effect transistor (FET) having a protrusive semiconductor layer protruding from a substrate plane, a gate electrode formed so as to straddle the protrusive semiconductor layer, a gate insulating film between the gate electrode and the protrusive semiconductor layer, and source and drain regions provided in the protrusive semiconductor layer, wherein the semiconductor device has on a semiconductor substrate an element forming region having a Fin type FET, a trench provided on the semiconductor substrate for separating the element forming region from another element forming region, and an element isolation insulating film in the trench; the element forming region has a shallow substrate flat surface formed by digging to a depth shallower than the bottom surface of the trench and deeper than the upper surface of the semiconductor substrate, a semiconductor raised portion protruding from the substrate flat surface and formed of a p

Abstract: Disclosed is a semiconductor device and method of fabricating the same. The device is disposed on a substrate, including a fin constructed with first and second sidewalls, a first gate line formed in the pattern of spacer on the first sidewall of the fin, and a second gate line formed in the pattern of spacer on the second sidewall of the fin. First and second impurity regions are disposed in the fin. The first and second impurity regions are isolated from each other and define a channel region in the fin between the first and second gate lines.

Abstract: A method is provided for making a semiconductor device, which comprises (a) providing a semiconductor structure comprising a top gate (228) and a bottom gate (240); (b) creating first, second and third openings in the semiconductor structure, wherein the first opening exposes a portion of the bottom gate; (c) filling the first, second and third openings with a conductive material, thereby forming source (258) and drain (260) regions in the second and third openings and a conductive region (253) in the first opening; and (d) forming an electrical contact (278) to the conductive region.

Abstract: A method for manufacturing a fin transistor includes forming a trench by etching a semiconductor substrate. A flowable insulation layer is filled in the trench to form a field insulation layer defining an active region. The portion of the flowable insulation layer coming into contact with a gate forming region is etched so as to protrude the gate forming region in the active region. A protective layer over the semiconductor substrate is formed to fill the portion of the etched flowable insulation layer. The portion of the protective layer formed over the active region is removed to expose the active region of the semiconductor substrate. The exposed active region of the semiconductor substrate is cleaned. The protective layer remaining on the portion of the etched flowable insulation layer is removed. Gates are formed over the protruded gate forming regions in the active region.

Abstract: The invention relates to a method of fabricating a CMOS device, comprising providing a semiconductor substrate (101) having therein a layer of insulating material (102), the method comprising providing a layer (106) of a first material over the insulating layer (102), the thickness of the layer (106) of the first material being less in a first region (103) for supporting a first active device than in a second region (104) for supporting a second active device. A layer (107) of a second material is then deposited over the layer (106) of a first material, and the structure is then subjected to a thermal treatment to alloy the first and second materials. The portion of the layers over the first region is entirely alloyed, whereas the portion of the layers over the second region is not, so that a portion (109) of the layer (106) of the first material remains.

Abstract: A dual polysilicon gate of a semiconductor device includes a substrate having a first region, a second region, and a third region, a channel region with a recessed structure formed in the first region of the substrate, a gate insulating layer formed over the substrate, a first polysilicon layer filled into the channel region, and formed over the gate insulating layer of the first and second regions, a second polysilicon layer formed over the gate insulating layer of the third region, and an insulating layer doped with an impurity, and disposed inside the first polysilicon layer in the channel region.

Abstract: In a semiconductor device including a multi-gate MIS transistor having a channel on a plurality of surfaces, a gate electrode is formed on a gate insulating film on side surfaces of an island-like semiconductor layer formed along a given direction on an insulating film, and source/drain electrodes are formed in contact with the semiconductor layer. The semiconductor layer has a plurality of side surfaces along the given direction. All angles formed by adjacent side surfaces are larger than 90°. A section perpendicular to the given direction is vertically and horizontally symmetrical.

Abstract: A method for making a semiconductor device with at least two gate regions. The method includes providing a substrate region including a surface. Additionally, the method includes forming a source region in the substrate region by at least implanting a first plurality of ions into the substrate region and forming a drain region in the substrate region by at least implanting a second plurality of ions into the substrate region. The drain region and the source region are separate from each other. Moreover, the method includes depositing a gate layer on the surface and forming a first gate region and a second gate region on the surface.

Abstract: In a semiconductor device having line type active regions and a method of fabricating the semiconductor device, the semiconductor device includes a device isolation layer which defines the line type active regions in a in a semiconductor substrate. Gate electrodes which are parallel to each other and intersect the line type active regions are disposed over the semiconductor substrate. Here, the gate electrodes include both a device gate electrode and a recessed device isolation gate electrode. Alternatively, each of the gate electrodes is constituted of a device gate electrode and a plan type device isolation gate electrode, and a width of the plan type device isolation gate electrode greater than a width of the device gate electrode.

Abstract: A method for making a semiconductor device comprises providing a first wafer and providing a second wafer having a first side and a second side, the second wafer including a semiconductor structure, a first storage layer, and a layer of gate material, wherein the first storage layer is located between the semiconductor structure and the layer of gate material and closer to the first side of the second wafer than the semiconductor structure. The method further includes bonding the first side of the second wafer to the first wafer and cleaving away a first portion of the semiconductor structure to leave a layer of the semiconductor structure after the bonding. The method further includes forming a second storage layer over the layer of the semiconductor structure and forming a top gate over the second storage layer.

Abstract: A nonvolatile semiconductor memory includes a plurality of memory cell transistors configured with a first floating gate, a first control gate, and a first inter-gate insulating film each arranged between the first floating gate and the first control gate, respectively, and which are aligned along a bit line direction; device isolating regions disposed at a constant pitch along a word line direction making a striped pattern along the bit line direction; and select gate transistors disposed at each end of the alignment of the memory cell transistors, each configured with a second floating gate, a second control gate, a second inter-gate insulator film disposed between the second floating gate and the second control gate, and a sidewall gate electrically connected to the second floating gate and the second control gate.

Abstract: A method forms a nonvolatile memory device using a semiconductor substrate. A charge storage layer is formed overlying the semiconductor substrate and a layer of gate material is formed overlying the charge storage layer to form a control gate electrode. A protective layer overlies the layer of gate material. Dopants are implanted into the semiconductor substrate and are self-aligned to the control gate electrode on at least one side of the control gate electrode to form a source and a drain in the semiconductor substrate on opposing sides of the control gate electrode. The protective layer prevents the dopants from penetrating into the control gate electrode. The protective layer that overlies the layer of gate material is removed. Electrical contact is made to the control gate electrode, the source and the drain. In one form a select gate is also provided in the memory device.

Abstract: A double-gated fin-type field effect transistor (FinFET) structure has electrically isolated gates. In a method for manufacturing the FinFET structure, a fin, having a gate dielectric on each sidewall corresponding to the central channel region, is formed over a buried oxide (BOX) layer on a substrate. Independent first and second gate conductors on either sidewall of the fin are formed and include symmetric multiple layers of conductive material. An insulator is formed above the fin by either oxidizing conductive material deposited on the fin or by removing conductive material deposited on the fin and filling in the resulting space with an insulating material. An insulating layer is deposited over the gate conductors and the insulator. A first gate contact opening is etched in the insulating layer above the first gate. A second gate contact opening is etched in the BOX layer below the second gate.

Abstract: The present invention provides, in one embodiment, a process for forming a dual work function metal gate semiconductor device (100). The process includes providing a semiconductor substrate (105) having a gate dielectric layer (110) thereon and a metal layer (205) on the gate dielectric layer. A work function of the metal layer is matched to a conduction band or a valence band of the semiconductor substrate. The process also includes forming a conductive barrier layer (210) on a portion (215) of the metal layer and a material layer (305) on the metal layer. The metal layer and the material layer are annealed to form a metal alloy layer (405) to thereby match a work function of the metal alloy layer to another of the conduction band or the valence band of the substrate. Other embodiments of the invention include a dual work function metal gate semiconductor device (900) and an integrated circuit (1000).

Abstract: A method of forming capacitorless DRAM over localized silicon-on-insulator comprises the following steps: A silicon substrate is provided, and an array of silicon studs is defined within the silicon substrate. An insulator layer is defined atop at least a portion of the silicon substrate, and between the silicon studs. A silicon-over-insulator layer is defined surrounding the silicon studs atop the insulator layer, and a capacitorless DRAM is formed within and above the silicon-over-insulator layer.

Abstract: A doubled gate, dynamic storage device and method of fabrication are disclosed. A back (bias gate) surrounds three sides of a semiconductor body with a front gate disposed on the remaining surface. Two different gate insulators and gate materials may be used.

Abstract: A method, and corresponding transistor structure are provided for protecting the gate electrode from an underlying gate insulator. The method comprises: forming a gate insulator overlying a channel region; forming a first metal barrier overlying the gate insulator, having a thickness of less than 5 nanometers (nm); forming a second metal gate electrode overlying the first metal barrier, having a thickness of greater than 10 nm; and, establishing a gate electrode work function exclusively responsive to the second metal. The second metal gate electrode can be one of the following materials: elementary metals such as p+ poly, n+ poly. Ta, W, Re, RuO2, Pt, Ti, Hf, Zr, Cu, V, Ir, Ni, Mn, Co, NbO, Pd, Mo, TaSiN, and Nb, and binary metals such as WN, TaN, and TiN. The first metal barrier can be a binary metal, such as TaN, TiN, or WN.

Abstract: A dual-gate device is formed over and insulated from a semiconductor substrate which may include additional functional circuits that can be interconnected to the dual-gate device. The dual-gate device includes two semiconductor devices formed on opposite surfaces of a common active semiconductor region which is provided a thickness and material sufficient to isolate the semiconductor devices from electrostatically interacting. In one embodiment, one of the semiconductor devices includes a charge storing layer, such as an ONO layer. Such a dual-gate device is suitable for use in a non-volatile memory array.

Abstract: There is provided a method for forming a gate using a gate layout of a semiconductor device. The layout includes an active region with a stepped side boundary, a plurality of gates crossing over the active region, and tabs attached to the gates on the side boundary of the active region, wherein two tabs adjacent by a topology of the stepped side boundary are disposed in an oblique direction. The gates can be patterned.

Abstract: A method of fabricating a dual-gate semiconductor device is provided in which silicidation of the source and drain contact regions (34, 36) is carried out after the first gate (12) is formed on part of a first surface (14) of a silicon body (16) but before forming a second gate (52) on a second surface (44) of the silicon body which is opposite the first surface. The first gate (12) serves as a mask to ensure that the silicided source and drain contact regions are aligned with the silicon channel (18). Moreover, by carrying out the silicidation at an early stage in the fabrication, the choice of material for the second gate is not limited by any high-temperature processes. Advantageously, the difference in material properties at the second surface of the silicon body resulting from silicidation enables the second gate to be aligned laterally between the silicide source and drain contact regions.

Abstract: A switch element includes a switch device having a drain, a source and a plurality of gates, and at least one additional interconnect located between the plurality of gates, the additional interconnect operative to establish a constant potential between the at least two gates.

Abstract: A field effect transistor with a fin structure having a first and a second source/drain region; a body region formed within the fin structure and between the first and the second source/drain region; a metallically conductive region formed within a part of the first source/drain region, the metallically conductive region being adjacent to the body region or to a lightly doped region disposed between the body region and the first source/drain region; and a current ballasting region formed within a part of the second source/drain region.

Abstract: A flash memory device of SONOS structure and a method for fabricating the same, and programming and erasing operation methods, to improve reliability such as endurance and retention, are disclosed, which includes a first conductive type semiconductor substrate; an ONO layer on the semiconductor substrate; a first control gate on the ONO layer; second and third control gates on the ONO layer at both sides of the first control gate; and source and drain regions in the surface of the semiconductor substrate at both sides of the second and third control gates.

Abstract: A method of fabricating a tri-gate semiconductor device comprising a semiconductor body having an upper surface and side surfaces and a metal gate that has an approximately equal thickness on the upper and side surfaces. Embodiments of a tri-gate device with conformal physical vapor deposition workfunction metal on its three-dimensional body are described herein. Other embodiments may be described and claimed.

Abstract: A semiconductor device according to an embodiment of the present invention has a gate electrode which is formed on a semiconductor substrate via a gate insulating film, and which has a slit portion; side wall films formed at both side faces of the gate electrode and at side walls of the slit portion, and which fill an interior of the slit portion and cover the gate insulating film directly beneath the slit portion; and an interlayer insulating film formed to cover the gate electrode and the side wall films.

Abstract: A method, structure and alignment procedure, for forming a finFET. The method including, defining a first fin of the finFET with a first mask and defining a second fin of the finFET with a second mask. The structure including integral first and second fins of single-crystal semiconductor material and longitudinal axes of the first and second fins aligned in the same crystal direction but offset from each other. The alignment procedure including simultaneously aligning alignment marks on a gate mask to alignment targets formed separately by a first masked used to define the first fin and a second mask used to define the second fin.

Abstract: A part of the gate of a FINFET is replaced with a stress material to apply stress to the channel of the FINFET to enhance electron and hole mobility and improve performance. The FINFET has a SiGe/Si stacked gate, and before silicidation the SiGe part of the gate is selectively etched to form a gate gap that makes the gate thin enough to be fully silicidated. After silicidation, the gate-gap is filled with a stress nitride film to create stress in the channel and enhance the performance of the FINFET.

Abstract: A method of forming a semiconductor structure including a plurality of finFFET devices in which crossing masks are employed in providing a rectangular patterns to define relatively thin Fins along with a chemical oxide removal (COR) process is provided. The present method further includes a step of merging adjacent Fins by the use of a selective silicon-containing material. The present invention also relates to the resultant semiconductor structure that is formed utilizing the method of the present invention.

Abstract: A method of doping fins of a semiconductor device that includes a substrate includes forming multiple fin structures on the substrate, each of the fin structures including a cap formed on a fin. The method further includes performing a first tilt angle implant process to dope a first pair of the multiple fin structures with n-type impurities and performing a second tilt angle implant process to dope a second pair of the multiple fin structures with p-type impurities.

Abstract: A method of forming a dual gate fin-type field effect transistor (FinFET) structure patterns silicon fins over an insulator and patterns a gate conductor at an angle to the fins. The gate conductor is formed laterally adjacent to and over center portions of the fins. The gate conductor is planarized such that the gate conductor is separated into distinct gate conductor portions that are separated by the fins. These gate conductor portions include front gates and back gates. The front gates and the back gates alternate along the structure, such that each fin has a front gate on one side and a back gate on the opposite side. Then front gate wiring is formed to the front gates and back gate wiring is formed to the back gates.

Abstract: An integrated circuit structure has a buried oxide (BOX) layer above a substrate, and a first-type fin-type field effect transistor (FinFET) and a second-type FinFET above the BOX layer. The second region of the BOX layer includes a seed opening to the substrate. The top of the first-type FinFET and the second-type FinFET are planar with each other. A first region of the BOX layer below the first FinFET fin is thicker above the substrate when compared to a second region of the BOX layer below the second FinFET fin. Also, the second FinFET fin is taller than the first FinFET fin. The height difference between the first fin and the second fin permits the first-type FinFET to have the same drive strength as the second-type FinFET.

Abstract: A method for forming transistors with mutually-aligned double gates. The method includes the steps of (a) providing a wrap-around-gate transistor structure, wherein the wrap-around-gate transistor structure includes (i) semiconductor region, and (ii) a gate electrode region wrapping around the semiconductor region, wherein the gate electrode region is electrically insulated from the semiconductor region by a gate dielectric film; and (b) removing first and second portions of the wrap-around-gate transistor structure so as to form top and bottom gate electrodes from the gate electrode region, wherein the top and bottom gate electrodes are electrically disconnected from each other.

Abstract: The present invention provides a method of fabricating a microelectronics device. In one aspect, the method comprises depositing a protective layer (510) over a spacer material (415) located over gate electrodes (250) and a doped region (255) located between the gate electrodes (250), removing a portion of the spacer material (415) and the protective layer (510) located over the gate electrodes (250). A remaining portion of the spacer material (415) remains over the top surface of the gate electrodes (250) and over the doped region (255), and a portion of the protective layer (510) remains over the doped region (255). The method further comprises removing the remaining portion of the spacer material (415) to form spacer sidewalls on the gate electrodes (250), expose the top surface of the gate electrodes (250), and leave a remnant of the spacer material (415) over the doped region (255).

Abstract: A method is provided for obtaining extremely fine pitch N-type and P-type stripes that form the voltage blocking region of a superjunction power device. The stripes are self-aligned and do not suffer from alignment tolerances. The self-aligned, fine pitch of the alternating stripes enables improvements in on-state resistance, while ensuring that the superjunction device is fully manufacturable. Only one masking step is required to fabricate the alternating N-type and P-type stripes.

Abstract: A substrate supporting a portion of a semiconductor material is used to produce a field-effect transistor. A portion of a temporary material lies between the portion of semiconductor material and the substrate. A gate is formed, which comprises an upper part in rigid connection with the portion of semiconductor material, and at least one bearing part settled on the substrate. The temporary material is removed and replaced with an electrically insulating material. During removal and replacement of the temporary material, the portion of semiconductor material is held in place relative to the substrate by the gate.

Abstract: An apparatus and method is disclosed for determining polysilicon conductor width for 3-dimensional field effect transistors (FinFETs). Two or more resistors are constructed using a topology in which polysilicon conductors are formed over a plurality of silicon “fins”. A first resistor has a first line width. A second resistor has a second line width. The second line width is slightly different than the first line width. Advantageously, the first line width is equal to the nominal design width used to make FET gates in the particular semiconductor technology. Resistance measurements of the resistors and subsequent calculations using the resistance measurements are used to determine the actual polysilicon conductor width produced by the semiconductor process. A composite test structure not only allows calculation of the polysilicon conductor width, but provides proof that differences in the widths used in the calculations do not introduce objectionable etching characteristics of the polysilicon conductors.

Abstract: A fin field effect transistor (fin FET) is formed using a bulk silicon substrate and sufficiently guarantees a top channel length formed under a gate, by forming a recess having a predetermined depth in a fin active region and then by forming the gate in an upper part of the recess. A device isolation film is formed to define a non-active region and a fin active region in a predetermined region of the substrate. In a portion of the device isolation film a first recess is formed, and in a portion of the fin active region a second recess having a depth shallower than the first recess is formed. A gate insulation layer is formed within the second recess, and a gate is formed in an upper part of the second recess. A source/drain region is formed in the fin active region of both sides of a gate electrode.

Abstract: Provided is a multiple-gate metal oxide semiconductor (MOS) transistor and a method for manufacturing the same, in which a channel is implemented in a streamline shape, an expansion region is implemented in a gradually increased form, and source and drain regions is implemented in an elevated structure by using a difference of a thermal oxidation rate depending on a crystal orientation of silicon and a geographical shape of the single-crystal silicon pattern. As the channel is formed in a streamline shape, it is possible to prevent the degradation of reliability due to concentration of an electric field and current driving capability by the gate voltage is improved because the upper portion and both sides of the channel are surrounded by the gate electrodes. In addition, a current crowding effect is prevented due to the expansion region increased in size and source and drain series resistance is reduced by elevated source and drain structures, thereby increasing the current driving capability.

Abstract: The invention pertains to thin film constructions comprising NVRAM devices built over a versatile substrate base. In particular aspects, a device includes a body region, and further include first and second diffusion regions formed in the body region. A channel region is in the body region between the first and second diffusion regions. A gate insulator stack is above the channel region, and a gate is over the gate insulator stack. The gate insulator stack includes a floating plate charge center which is electrically connected to the second diffusion region. The memory device includes a diode which connects the body region to the second diffusion region such that the floating plate is charged when the diode is reversed biased. The invention also includes electronic systems comprising novel TFT-based NVRAM devices.

Abstract: A method of forming a dual gate dielectric layer increases a performance of a semiconductor device by using a dielectric layer having a high dielectric constant, including forming a first dielectric layer having a predetermined thickness on a semiconductor substrate; removing the first dielectric layer formed on a second region, but leaving this layer on a first region; and forming a second dielectric layer having a dielectric constant higher than that of the first dielectric layer, on the first and second regions.

Abstract: A method for manufacturing a transistor is provided. The transistor has a substrate with an insulator on the substrate. A structure on the insulator having a structure sidewall is provided with spacers covering a portion of the structure sidewall. An exposed portion of the structure sidewall is activated, and a conformal layer of metal or metal containing material is deposited on the exposed portion of the structure sidewall. The metal or metal containing material is annealed to diffuse into the exposed portion of the structure sidewall to form a salicide.

Abstract: To reduce a current loss through a channel and improve electron mobility, a first semiconductor layer and a second semiconductor layer (sequentially formed on a semiconductor substrate) have different lattice properties. The first semiconductor layer and the second semiconductor layer may be etched to form a first semiconductor pattern. A third semiconductor layer having a lattice property substantially identical to that of the first semiconductor layer may be formed over the first semiconductor pattern. The third semiconductor layer may then be etched to form a second semiconductor pattern. A gate may be formed on the second semiconductor pattern. The contact surface between the second semiconductor pattern and the gate pattern may consequently increased to reduce a current loss. Further, the lattice properties may be changed to improve electron mobility of the semiconductor layers.