44 results about "Ge element" patented technology

The invention provides a method for epitaxially growing SiGe epitaxial layers. The method is applied to filling the SiGe epitaxial layers in source and drain electrode regions of a PMOS (P-channel metal oxide semiconductor), and reaction gas containing Ge elements and carbonaceous gas are simultaneously filled into a reaction chamber, so that the carbonaceous SiGe epitaxial layers are selectively and epitaxially grown on surfaces of source and drain electrode regions of the surface of a silicon substrate. The method has the advantages that on the premise that contents of Ge elements in the SiGe epitaxial layers are guaranteed, critical thicknesses of the SiGe epitaxial layers are increased, strain relaxation is avoided, and the carrier mobility of the PMOS is improved.

The invention discloses an infrared night-vision goggle based on a GeSn infrared detector, and mainly aims to solve the problem that the existing infrared night-vision goggle is of low light sensing efficiency. The infrared night-vision goggle comprises an optical system, a detector, a signal processor and a display. The detector is a GeSn infrared detector, and comprises a substrate (1), a lower electrode (2), an absorption area (3) and an upper electrode (4), wherein the absorption area (3) is made of a GeSn material of which the general formula is Ge1-xSnx, x is a component of Sn, and 0<=x<=0.25. As the Sn element is added to the Ge element to form a relaxation intrinsic GeSn single crystal, the energy band structure of GeSn is changed from direct band gap to direct band gap while the forbidden bandwidth is decreased. Therefore, the light sensing frequency is increased, the red shift of the absorption edge is adjustable, and the light sensing efficiency and absorption wavelength range of the infrared night-vision goggle are improved.

The invention relates to a novel Ge-heavily-doped photosensitive fiber, which is doped with 46% to 54% Ge element in the core layer of an optical fiber with an NA value of 0.25 to 0.31. The Ge-heavily-doped photosensitive fiber has large mode field diameter and small attenuation, and can satisfy the requirement for signal transmission and sensing, so that a fiber grating can be directly etched on a certain section of an optical fiber segment and the rest section serves as the optical fiber for transmitting signal. The invention has a significant characteristic that the photosensitive fiber has very high photosensitive performance, and the fiber grating can be directly etched in the core of the optical fiber without hydrogen loading treatment, etc. The invention can save a great amount of processing program and time and can provide excellent sensing element for an optical fiber sensor system.

The invention discloses an oxidation-resistant SmCoX-Y(SiaGebSnc)Y high-temperature permanent-magnet material for an aeroengine and a preparation method thereof. The expression formula of the permanent-magnet material is SmCoX-Y(SiaGebSnc)Y, wherein the atom number of X is 5.0-8.5 and the atom number of Y is 0.01-1.90; and a+b+c=1, the atom number of a is 0.20-0.98, the atom number of b is 0.01-0.70 and the atom number of c is 0.01-0.10. In the invention, Si, Ge and Si elements are doped in SmCo7 alloy, and the ratio of three elements (Si, Ge and Sn) is properly adjusted to achieve the purposes of simultaneously stabilizing the structure of TbCu7 and improving the high-temperature oxidation resistant capacity of a magnet. The Si element is doped, so that the formation of a TbCu7 phase canbe promoted and the high-temperature oxidation resistance of the material can be improved; the Ge element is doped, so that the growth of crystal grains in the sintering process can be inhibited; andthe Sn element is doped, so that the sintering temperature can be reduced, the sintering efficiency can be improved and the mechanical performance of the material can be enhanced at the same time.

The invention provides a PMOS transistor and a manufacturing method of the PMOS transistor. When source electrode areas and drain electrode areas of the PMOS transistor are formed, a method that a first stress adjusting layer, a second stress adjusting layer and a stress maintaining layer sequentially grow in an epitaxial mode is adopted. The lattice constant of the first stress adjusting layer and the lattice constant of the second stress adjusting layer gradually increase. When the second stress adjusting layer is formed in an epitaxial mode, an element with the lattice constant larger than that of the Ge element for doping, so that the second stress adjusting layer forms most of the source electrode areas and the drain electrode areas, and larger pressure stress is provided for a channel so that the channel can have higher carrier mobility and work current of a device can be improved; the first stress adjusting layer between the second stress adjusting layer and a substrate serves as a stress buffering layer, and defects caused by too large lattice mismatch between the second stress adjusting layer and the substrate are reduced; a sandwich structure formed by the first stress adjusting layer and the second stress adjusting layer which are spaced is adopted, so that the defects caused by too large lattice mismatch between the second stress adjusting layer and the substrate are further reduced.

A quartz cladding large-power-transmission dispersion optical fiber and a manufacturing method thereof relate to the technical field of optical communication and related sensing devices. The dispersion optical fiber is composed of a core layer, a first quartz cladding and a second quartz cladding which are successively arranged from inside to outside. The core layer is doped with Ge element; the refractivity of the core layer changes in a gradual manner; and furthermore distribution power exponent is 1.5-3.3. The first quartz cladding contains bubbles and has a light scattering function. The refractivity of the second quartz cladding is higher than that of the first quartz cladding. The quartz cladding large-power-transmission dispersion optical fiber and the manufacturing method have advantages of enduring relatively high power and relatively high temperature, improving stability and reliability of the optical fiber, and effectively settling a color change problem of the optical fiber in illumination.

The invention discloses fluorescent ceramic as well as a preparation method and application thereof. The fluorescent ceramic is selected from at least one of substances with a composition general formula shown in a formula I, and the formula I is Lu<3-x-y>Ce<x>M<y>Al<5-y>Q<y>O12, wherein M represents a first co-doped element, the first co-doped element is selected from at least one of alkaline earth metal elements, Q represents a second co-doped element, the second co-doped element is selected from at least one of a Si element and a Ge element, x is more than or equal to 0.0001 and less than or equal to 0.3, and y is more than or equal to 0 and less than or equal to 2. Charge balance is realized through equivalent common doping of doped M<2+> and Q<4+> ions, so that variable-valence Ce<3+>ions in the fluorescent ceramic are inhibited from being converted into Ce<4+> ions, and the fluorescent ceramic is mostly composed of Ce<3+> light-emitting ions. The fluorescent ceramic has the characteristics of high density, good laser saturation performance, high luminous efficiency and the like, can be used as a key material of a color converter, and has a huge application potential in the field of high-power laser illumination.

The invention provides an MOSFET with a SiGe channel and a forming method of the MOSFET. The forming method includes the following steps of providing a substrate with a Si layer at the top, injecting atoms, molecules, ions or plasmas containing Ge elements into the surface layer of the Si layer so that the SiGe layer can be formed, forming a gate stacking structure on the upper portion of the SiGe layer, and forming a source and a drain on the two sides of the gate stacking structure. According to the forming method of the MOSFET, the MOSFET with the SiGe channel can be formed, the SiGe channel is thin, crystalline quality is good, and accordingly the MOSFET has good electrical property and the method has the advantages of being simple, easy to carry out and low in cost.

The invention provides a phase change thin film structure, a phase change memory unit, a manufacturing method thereof and a phase change memory. The phase change thin film structure comprises Cr layers and GexTe100-x layers, wherein 0<x<100, and the Cr layers and the GexTe100-x layers are alternately stacked in turn. The phase change thin film structure disclosed in the invention can continuouslyundergo two phase changes during a temperature rise process; in an early stage of temperature rise, the GexTe100-x layer changes from an amorphous state to a polycrystalline state, and a reversible high-resistance state and low-resistance state change is accompanied; in continuous temperature rise, a Cr2Ge2Te6 layer is formed at the interface between the Cr layer and the GexTe100-x layer, partialCr enters the GexTe100-x layer under interfacial diffusion at high-temperature induction to replace partial Ge elements in the GexTe100-x layer, and a reversible low-resistance state and high-resistance state change is accompanied; and when the temperature rises continuously, high-resistance state GexTe100-x amorphous state can be returned.

The invention relates to a method for constructing an In2S3 impurity band semiconductor. An In2S3 semiconductor serves as an index compound, a Ge element is adopted for doping the In position of the In2S3 semiconductor, and the In2S3 impurity band semiconductor is obtained. Compared with the prior art, according to the In2S3 impurity band semiconductor, In2S3 with the excellent performance is adopted as a substrate material, the VI group element Ge is adopted for doping the In positon of the In2S3 semiconductor, thus a strip of an impurity band is introduced in an index band gap, the electrontransition path is increased, the absorption spectrum is broadened, optical absorption of raw materials is enhanced, thus the In2S3 semiconductor can be directly used as a solar cell adsorption material, and practical significance is achieved for development of solar energy sources; the theoretical calculated absorption spectrum of the In2S3 and Ge doped In2S3 shows that an intrinsic semiconductorhas only one absorbing edge, after the Ge is doped, a novel absorbing edge occurs, and an absorbing curve starts being enhanced significantly in the energy area lower than the band gap. According tothe Ge doped In2S3 semiconductor material, the preparation method is simple, and industrial large-scale production can be achieved.

The invention relates to a Ge-containing low-quenching sensitive aluminum alloy. Aluminum alloy is subjected to micro-Ge alloying treatment; based on the characteristic that binding energy of Ge element and vacancy is far more than that of elements of Zn, Mg, Cu and the like and the vacancy is utilized, the Ge element, when solid solution is quenched, is added into the inside of the alloy and is preferentially combined with the vacancy to prevent the diffusion of Zn, Mg, Cu and other solute atoms of the alloy at a low solid solution quenching speed and the precipitation of a coarse second phase; and therefore, the full hardening of the aluminum alloy is improved effectively, the quenching sensitivity of the aluminum alloy is reduced, and a quenching tissue with full solid solution is provided for obtaining dispersion-strengthened phase in subsequent aging. The Ge-containing low-quenching sensitive aluminum alloy can effectively reduce the quenching sensitivity of the aluminum alloy and improves the full hardening of the aluminum alloy, the saturation of the solute atom solid solution of the alloy at the low quenching speed and the mechanical property after the aging treatment. The Ge-containing low-quenching sensitive aluminum alloy provides a reliable aluminum alloy structural material for meeting the needs for large-scale heavy plates and large members in aerospace and other fields.

The invention is a measuring method for fiber stress double-refraction value of stress deflection and maintaining fiber in fiber interference communication and fiber sensor fields. The technology includes following steps: selects out the samples in stress area and core area, measures the content of B element in stress sample, measures the content of element Ge in core area; plates conductive film with thickness from 1 micron to 2 micron on the end surface of the fiber, scans the surface used as the atom lining by the electron probe device and carries on line scan to the Ge element, eliminates the impurities and spots on the surface; the image is inputted into the MATLAB project software, works out the stress double-refraction value through stress double-refraction formula and stress area impurities density.

The invention provides a fin-shaped field effect transistor with a SiGe channel and a forming method of the fin-shaped field effect transistor. The forming method includes the following steps of providing a substrate, forming a Si fin-shaped structure on the upper portion of the substrate, injecting atoms, molecules, ions or plasmas containing Ge elements into the Si fin-shaped structure so that the SiGe layer can be formed, and forming a gate stacking structure on the upper portion of the SiGe layer. According to the forming method, the FinFET with the SiGe channel can be formed, the SiGe channel is thin and good in quality, and accordingly the forming method has the advantages of being simple, easy to carry out and low in cost.

The invention provides a FinFET with a SiGe source region and a SiGe drain region and a forming method of the FinFET. The method includes the following steps of providing a substrate, forming a Si fin-shaped structure on the upper portion of the substrate, forming gate stacking or a fake gate on the upper portion of the Si fin-shaped structure, forming openings of the source region and the drain region on the two sides of the gate stacking or the fake gate, exposing the Si fin-shaped structure at the opening positions, and injecting atoms, molecules, ions or plasmas containing Ge elements into the Si fin-shaped structure so that SiGe layers can be formed at the opening positions. According to the forming method of the FinFET, the FinFET with the SiGe source region and the SiGe drain region can be formed, the SiGe source region and SiGe drain region are thin, crystalline quality is good, and accordingly the FinFET has good electrical property, and the method has the advantages of being simple, easy to carry out and low in cost.

The invention discloses a low quenching sensitive aluminum alloy added with Ag and Ge at the same time. The aluminum alloy is subjected to alloying treatment of trace Ag and Ge elements. On the one hand, the Ag and a vacancy have higher binding energy by using the characteristic that the binding energy of the Ge element and the vacancy is far greater than that of elements such as Zn, Mg, Cu and the like and the vacancy, and the Ge and Ag elements added into the alloy are first bond with the vacancy during solid solution quenching so as to prevent the dispersion of solvent atoms of Zn, Mg, Cu and the like in the alloy and the separation of a thick second phase at a low solid solution quenching speed, effectively improve the quenching property of the aluminum alloy, reduce the quenching sensitivity of the aluminum alloy and provide a complete solid solution quenching tissue for obtaining a dispersed strengthening phase for follow-up ageing; and on the other hand, the added Ag can play a role in reinforcement when the Ge is added by using the effect that the Ag can produce solid solution reinforcement and separation promotion in the aluminum alloy. A low quenching sensitive aluminum alloy structural material is provided for large-scale thick plates and large members in aerospace and other fields.

The invention relates to a heating electrode material for phase varying memory and the preparing method thereof, where the heating electrode material is a heating electrode material at least containing Ge element whose general formula is one of GexWyN1-x-y, GexTiyN1-x-y, GexWyO1-x-y and GexTiyO1-x-y, where x and y are atomic percents of elements and 0ú“xíœ1, 0íœyú“1, and 0ú“x+yíœ1; the preparing method adopts any one of the processes: sputtering, evaporating, atomic layer deposition, chemical vapour deposition, and metallic organic matter thermal decomposition or laser auxiliary deposition, and as compared with traditional heating electrode materials such as W, TiN, TiON and TiAlN, the Ge-base heating electrode material of the invention has advantages of adhesive property to phase varying material, high resistance, etc, able to raise heating efficiency of devices and reduce device power losses.

The invention discloses Sn-Sb-Se chalcogenide glass. The formula of the chalcogenide glass is SnxSbySez, wherein x, y and z respectively represent the mole number of Sn, Sb and Se, x=6-12, y=10-20, and z=68-82. In the microstructure of the chalcogenide glass, the percentage of the bond number of Sn-Se bonds accounting for the total chemical bond number is 16.45-32.67%, the percentage of the bond number of Sb-Se bonds accounting for the total chemical bond number is 20.08-58.37%, and the balance is the percentage of the bond number of Se-Se bonds accounting for the total chemical bond number. The Sn-Sb-Se chalcogenide glass has the advantages that the Sn-Sb-Se chalcogenide glass does not contain toxic As element and expensive Ge element and is simple and practical in preparation method, the forming area of the Sn-Sb-Se chalcogenide glass mainly concentrates on a selenium-rice area, the refractive index of the Sn-Sb-Se chalcogenide glass at a 4-micrometer waveband position is 2.59-2.86, third-order nonlinear refractive index can reach up to 10.15*10<-18>m<2> / W, the Sn-Sb-Se chalcogenide glass is good in mid-infrared and far-infrared transmission capacity and near-infrared transmission capacity, and a foundation is laid for the infrared device design and manufacturing of the Sn-Sb-Se chalcogenide glass and application of the Sn-Sb-Se chalcogenide glass to the optical field.

The invention discloses an oxide thin-film, a thin-film transistor and a preparation method thereof. The invention relates to the technical field of the thin-film transistor. In the thin-film transistor, the chemical general formula of the oxide thin-film of the oxide thin-film channel layer is In-X-Zn-O, wherein X is Si element, Ge element, La element or Y element; a gate electrode is arranged over a substrate; a gate insulation layer is arranged at the gate electrode, and over the portion of the substrate not covered by the gate electrode; the oxide thin-film channel layer is arranged over the gate insulation layer; a source electrode area is arranged at one side of the upper of the oxide thin-film channel layer; and the leakage electrode area is arranged at the side of the upper of the oxide thin-film channel layer. Based on the In-X-Zn-O thin-film transistor, the invention can enhance the inhibiting ability of the oxide thin-film channel layer to the formation of a charge carrier, improves the crystallization temperature of a crystal so as to improve the consistency of element preparation, and weakens the effects of the oxide thin-film channel layer to the threshold voltage, leakage current Ioff and on-off time ratio of the thin-film transistor.

The invention relates to the technical field of metal alloy materials, and particularly relates to a preparation method of casting high-strength rapid-corrosion magnesium alloy. The method comprises the following steps: (1) correspondingly preprocessing a magnesium ingot and an aluminum ingot; (2) preprocessing germanium particles; (3) smelting the preprocessed magnesium ingot and the aluminum ingot; (4) adding the germanium particles after smelting so as to obtain a smelted material; and (5) cooling the smelted material; then pouring; and naturally cooling the casting ingots until room temperature is reached, and thus obtaining the casting high-strength rapid-corrosion magnesium alloy, wherein the casting high-strength rapid-corrosion magnesium alloy comprises the following components inpercentage by weight: 2-8% of Al, 0.5-7% of Ge, and the balance magnesium. According to the method, the Al and Ge elements are fully utilized to improve the strength and corrosion rate of the magnesium alloy; the alloy elements of few types are added, and few alloy elements are added, so that the mechanical performance and the corrosion rate can be obviously improved.

The invention discloses a Ge-doped Mg2Si-base thermoelectric film and a preparation method thereof. A magnetron sputtering deposition process is employed for performing double-target cyclic sputtering and further for preparing a film with a lamination structure, and then vacuum annealing is employed for obtaining the Ge-doped Mg2Si-base thermoelectric film. The thermoelectricity performance of the Mg2Si-based material is improved by utilizing Ge doping and film low-dimension processing, the method is high in controllability. The Ge element doping amount can be adjusted by adjusting the sputtering power, the sputtering time ratio and other parameters. The doped Ge element uniformity is improved by employing heat treatment. The film possesses the advantages of strong binding force between the film and a substrate, uniform compact film, simple technology, low cost and the like, and possesses significant industrial application value.

The invention is concerned with a kind of phase change film material with chalcogenide in silicon series for phase change storage, belonging to micro-electronics technology field. Si element takes place of Ge element of TeaGebSb100-(a+b) alloy to form TeaGeb-cSicSb100-(a+b) alloy film, and a is from 48 to 60, b is from 8 to 40, the replace scalar c of Si is from 1 to 40 atom percent. This invention has higher crystal resistance than common Ge2Sb2Te5 phase change film, and more higher amorphous / crystalline state change ratio of resistance and more lower amorphous / crystalline state film thickness change ratio and lower melting point. This kind of storage has more higher open / close ratio and stability of piece to reduce writing current of storage and get storage multi-value with higher density.

The invention discloses an oxide near-infrared light-emitting material, a preparation method thereof and a light-emitting device. The near-infrared light-emitting material comprises an inorganic compound, wherein the chemical formula of the inorganic compound is AxByCzOqDp; wherein A is one or a combination of more than two of elements of Mg, Ca, Sr, Ba, Lu, Y, Gd or La; B is one or a combination of more than two of Sc, In, Ga, Mg, Zr, Ti, Hf, Sn, Lu, Y, Gd or La; C is one or a combination of more than two of Al, Si or Ge elements; O is an oxygen element; D is a Cr element; 0.7 < = x < = 1.3, 0.7 < = y < = 1.3, 1 < = Z < = 3, 5 < = q < = 7, and 0 < p < = 0.3. The emission peak wavelength of the near-infrared light-emitting material is about 930 nm, the half-peak width is about 210 nm, the near-infrared light-emitting material can be efficiently excited by blue light, and the chemical stability and the thermal stability are good.

The invention discloses a Ge (germanium) element compensation method for CdGeAs2 single crystal growth. The method adopts a growth device comprising a single crystal growth crucible, a germanium element compensation device and a six-temperature-zone growth furnace for controlling Ge element compensation for CdGeAs2 single crystal growth. A high-purity CdGeAs2 multi-crystal raw material is put in acrucible provided with a Ge element compensation device for vacuum sealing and then put in the six-temperature-zone growth furnace, CdGeAs2 single crystal growth and Ge element compensation are realized through accurate temperature control, so that Ge elements at the upper and lower ends of the grown single crystal are uniform, and the phenomenon of inconsistent properties formed by different Geelements in the single crystal is avoided. The method is easy to implement, the utilization rate of the single crystal is effectively increased, and the growth cost is reduced.

The invention relates to a heating electrode material for phase varying memory and the preparing method thereof, where the heating electrode material is a heating electrode material at least containing Ge element whose general formula is one of GexWyN1-x-y, GexTiyN1-x-y, GexWyO1-x-y and GexTiyO1-x-y, where x and y are atomic percents of elements and 0<x<=1, 0<=y<1, and 0<x+y<=1; the preparing method adopts any one of the processes: sputtering, evaporating, atomic layer deposition, chemical vapour deposition, and metallic organic matter thermal decomposition or laser auxiliary deposition, and as compared with traditional heating electrode materials such as W, TiN, TiON and TiAlN, the Ge-base heating electrode material of the invention has advantages of adhesive property to phase varying material, high resistance, etc, able to raise heating efficiency of devices and reduce device power losses.

The invention discloses an aluminum alloy low-temperature high-strength diffusion welding method based on a composite interlayer. According to the method, Zn and Ge elements are used for coordinated control, the melting point of the composite intermediate layer is effectively reduced, the welding temperature is effectively reduced, Mg2Ge strengthening phase precipitation is induced, the joint strength is remarkably improved, the SPS diffusion welding process is applied, the welding period is greatly shortened, and the high-pressure acting time is shortened. According to the low-temperature, low-deformation and high-strength diffusion welding method, through deep fusion of materials and the technology, the problem that after-welding low-deformation-rate control and high-strength connection of the 6061 aluminum alloy obtained through an existing connection technology are cooperatively regulated and controlled is effectively solved, and low-temperature, low-deformation and high-strength diffusion welding with the joint metallurgical bonding strength exceeding the after-welding base metal intrinsic strength and the after-welding deformation rate being only 2.23% is achieved.

The invention discloses an adsorbent for a germanium [68Ge] gallium [68Ga] generator, a preparation method of the adsorbent and the germanium [68Ge] gallium [68Ga] generator. The adsorbent is used for adsorbing the < 68 > Ge element; the adsorbent comprises a plurality of titanium dioxide particles, wherein the specific surface area of the plurality of titanium dioxide particles is 30 m < 2 > / g to 100 m < 2 > / g; the titanium dioxide particles are composed of a plurality of nanoparticles, and the average particle size of the plurality of nanoparticles is 10 nm to 100 nm; the nanoparticles comprise mesopores, and the pore diameter of the mesopores is 5 nm to 30 nm.

The invention provides germanium-doped uvarovite microwave dielectric ceramic as well as a preparation method and application thereof, and relates to the technical field of microwave dielectric ceramic materials. The invention provides germanium-doped uvarovite microwave dielectric ceramic. The chemical general formula of the germanium-doped uvarovite microwave dielectric ceramic is Ca3Cr2 (Si < 1-x > Ge < x >) 3O12, wherein x is the mole fraction of the Ge element, and x is larger than or equal to 0.025 and smaller than or equal to 0.4. The normal-pressure solid-phase reaction is combined with the gradient cold isostatic pressing process, the method is simple in process and non-toxic (dichromate is not used), a sintering aid does not need to be introduced, and the single-phase compact microwave dielectric ceramic with the high quality factor can be prepared at the normal pressure. The prepared germanium-doped uvarovite microwave dielectric ceramic realizes component regulation and control by partially replacing Si < 4 + > with Ge < 4 + >, so that the stability of the material is improved, and meanwhile, the germanium-doped uvarovite microwave dielectric ceramic has a relatively low dielectric constant (epsilon r = 7.67-8.66), a high quality factor (Q * f = 13871-39146 GHz) and a good temperature coefficient of resonance frequency (tau f =-41-36ppm / DEG C), and meets the strict requirements of 5G / 6G high-frequency communication devices on low loss and high stability.

The invention discloses chalcogenide glass which comprises an element Se, an element As, an element Ge and an element Te, the content of the element Se is 43 mol%-53 mol%, the content of the element As is 38 mol%-48 mol%, the content of the element Ge is 2 mol%-8 mol%, and the content of the element Te is 1 mol%-10 mol%. According to the chalcogenide glass disclosed by the invention, the chalcogenide glass can obtain a relatively low refractive index temperature coefficient under the condition of relatively low germanium element content by controlling the proportion of each element in the chalcogenide glass, so that the production cost of the chalcogenide glass is reduced, and the chalcogenide glass keeps relatively high refractive index, relatively high glass transition temperature and relatively high infrared transmittance; and compared with chalcogenide glass with high germanium content, the chalcogenide glass has higher refractive index.

A method of fabricating PMOS devices with embedded SiGe is disclosed. Prior to the selective epitaxial growth of SiGe, Ge element is implanted to the source / drain recesses and an annealing process is performed to form a strained SiGe alloy layer. Then, the strained SiGe alloy layer is used as a base layer on which another strained SiGe alloy layer is grown continually by an selective epitaxy process, so as to avoid a direct contact between the epitaxially grown strained SiGe alloy layer and the silicon substrate and reduce the defects formed at the SiGe / Si interfaces. Therefore, the stress can be applied to the PMOS channel regions without causing junction current leakage due to the defects at the SiGe / Si interfaces, which enhances the electrical performance of the PMOS devices. The fabrication method is also compatible with the conventional CMOS process.