Semiconductor device using insulator and metal phase change material, and method of manufacturing semiconductor device

Abstract

To provide a semiconductor device with a room temperature controllable phase change between a metal phase, which is a conductor, and an insulating phase that can be easily incorporated into large-scale semiconductor fabrication.SOLUTION: A semiconductor device 500 incorporates a phase change material MoxW1-xTe2 that may be a semiconducting channel 405 or may be part of a control terminal / gate (gate region 425) of a semiconductor. The phase change material is selectably in one of metal and insulator phases depending on whether a voltage field greater than a predetermined phase change field is present at the phase change material. The properties of the semiconductor are varied depending on the phase of the phase change material.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] Embodiments of the present invention relate generally to semiconductor devices, and more particularly to semiconductor devices that use insulator-semiconductor phase change materials that have an electric field-controllable phase change between a semiconducting phase and a metallic phase at room temperature. [Background technology]

[0002] Materials are known that change between semiconducting and metallic phases in response to substantial temperature or pressure changes, with the obvious constraint that they must be operated at temperatures different from room temperature and pressures different from ambient atmospheric pressure in order to induce and / or promote the phase change between the semiconducting and insulating states. Summary of the Invention [Problem to be solved by the invention]

[0003] One objective of embodiments of the present invention is to provide a semiconductor device with room temperature controllable phase change between a conducting metallic phase and an insulating phase that can be easily integrated into current large scale semiconductor manufacturing.

[0004] Yet another object of embodiments of the present invention is to provide embodiments that are compatible with typical silicon large scale manufacturing of semiconductor devices. [Means for solving the problem]

[0005] An exemplary semiconductor device is a phase change material, Mo, which may be a semiconductor channel and may be part of the control terminal or gate. x W 1-x The phase change material incorporates Te2. The phase change material can be controlled to exist in one of a metallic phase and an insulating phase depending on whether a voltage field greater than a predetermined electric field is present across the phase change material. The physical properties of the phase change material, particularly its electrical conductivity or lack thereof, vary substantially depending on the phase of the phase change material.

[0006] In one exemplary embodiment of a switch in a semiconductor device, a phase change material is used for the semiconductor channel, responsive to the phase change material being in its metallic phase in the on state and the phase change material being in its insulator phase in the off state. An externally controllable voltage difference applied across the semiconductor channel generates a field that controls the phase of the phase change material.

[0007] In another exemplary embodiment of a switch in a semiconductor device, a field effect transistor (FET) has a source region and a drain region spaced apart on its surface. A dielectric layer is disposed on the surface of the semiconductor channel between the source and drain regions, and a gate region is disposed on the opposing surface of the dielectric layer, the gate region being disposed between the source and drain regions. The source region, gate region, and drain region are each made of Mo. x W 1-x Metal contacts comprising a Te2 phase change material are disposed over the source, gate, and drain regions to facilitate electrical connection, and an externally controllable voltage difference generates a field that is applied across at least a portion of the phase change material to control the phase of the phase change material.

[0008] In a further exemplary embodiment of the switch in the semiconductor device, the FET includes an additional control terminal disposed between the gate region and the drain region, the additional control terminal being Mo x W 1-x Made of Te2 phase change material. An externally controllable voltage difference generates a field that is applied across the phase change material to control the phase of the phase change material between the metallic and insulating phases. The additional control terminal in the body layer acts as a shield to passivate traps at the surface of the semiconductor channel between the gate and drain regions. [Effects of the Invention]

[0009] The added control terminal in the insulator layer enhances the high frequency response of the FET by not presenting a physical active area adjacent to the gate region.

[0010] Features of exemplary embodiments of the present invention will become apparent from the following description, claims, and accompanying drawings. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a top view of one embodiment of an exemplary semiconductor device according to the present invention. [Figure 2] FIG. 2 is a cross-sectional view of another embodiment of a semiconductor device according to the present invention. [Figure 3] FIG. 3 is a graph showing an exemplary change in current flow with respect to a change in control voltage. [Figure 4] FIG. 4 is a representative cross-sectional view of an embodiment according to the present invention showing a point in the manufacturing process. [Figure 5] FIG. 5 is a representative cross-sectional view at a later processing step than that shown in FIG. [Figure 6] FIG. 6 is a representative cross-sectional view illustrating the completion of fabrication of the embodiment shown in FIG. [Figure 7] FIG. 7 is a representative cross-sectional view showing another embodiment according to the present invention. [Figure 8] FIG. 8 is a representative cross-sectional view illustrating a further embodiment according to the present invention. [Figure 9] FIG. 9 is a flow diagram illustrating steps in the manufacture of an embodiment in accordance with the present invention. [Figure 10] FIG. 10 is a schematic diagram illustrating an exemplary circuit that may be used to provide a voltage difference that creates a field sufficient to control the phase of a phase change material, as used in a FET embodiment. [Figure 11] FIG. 11 is a schematic diagram illustrating an exemplary circuit that may be used to provide a voltage difference that will generate a field sufficient to control the phase of a phase change material used as a switch in a semiconductor device that has an on or off state. DETAILED DESCRIPTION OF THE INVENTION

[0012] FIG. 1 illustrates a top view of one embodiment of a representative semiconductor device 100. A conventional substrate 105, such as a silicon, GaAs, InP, SiC, or sapphire substrate commonly used in the fabrication of field-effect transistors (FETs), has metal regions 110 and 140 disposed thereon. Interconnects 120 and 125, acting as metal contacts, are disposed on the top surface of substrate 105 and function to provide conductive connections to the left and right ends of phase-change region 130, which is disposed as vertical strips on the top surface of substrate 105 between interconnects 120 and 125. Metal regions 110 and 140 do not contact each other and are electrically isolated from phase-change region 130. Metal regions 110 and 140 facilitate the selectable application of voltage across phase-change region 130 and control whether the phase-change material is in the metallic or insulator phase, corresponding to the flow of current from interconnect 120 to interconnect 125.

[0013] Metal region 110 and metal region 140 provide a sandwich structure spaced apart from the lateral sides of phase change region 130. Metal region 110 and metal region 140 control the on operation of semiconductor device 100 when a predetermined voltage equal to or greater than the required phase change voltage is applied between the plates, for example, by a DC or AC voltage source (not shown), or control the off operation of semiconductor device 100 when no DC or AC voltage source (not shown) is applied between the plates. Metal region 110 and metal region 140 control the on or off operation of semiconductor device 100 when the predetermined voltages are equal, thereby forming the positive and negative voltage plates of a capacitor that controls the on or off operation of semiconductor device 100. The phase change material effectively functions as a phase change region 130. When a predetermined voltage is applied, the electric field that develops between the plates provides sufficient energy via the corresponding electric field to change the phase change region 130 from one of the insulator and metallic phases to the other. When no voltage (or a voltage less than the required phase change voltage) is applied across the plates, the other phase exists. Phase change materials can be fabricated to have stable static states of either the insulator or the metallic phase. The insulator phase corresponds to the switch as semiconductor device 100 being in the OFF state, and the metallic phase corresponds to the switch as semiconductor device 100 being in the ON state. This operation of the switch as semiconductor device 100 occurs while the temperature of semiconductor device 100 remains approximately constant at approximately room temperature, requiring no pressure change to facilitate switch operation as semiconductor device 100.

[0014] The phase change region 130 is a MoS2 layer that can change between an insulating phase and a metallic phase based on the presence or absence of an electric field created by a voltage difference of a few volts, for example, about 0.5 to 5 volts. x W 1-x It is preferable that the material is made of Te2. This operation does not require changes in temperature or pressure. Mo, where x in the composition formula varies between 0.66 and 1.0, is used. x W 1-x Te2 is used to enable effective operation of the semiconductor device 100. The ratio between Mo and W, as well as the distance between the control electrodes, determines the electric field required to cause a phase change.

[0015] FIG. 2 is a cross-sectional view of another exemplary embodiment of a switch as semiconductor device 200 according to the present invention. Metallic switch control contact 210 is disposed on substrate 205. Dielectric layer 215 covers the top surface of substrate 205. Phase change region 220 is disposed on the top surface of dielectric layer 215, substantially opposite switch control contact 210. Conductive interconnects 225 and 230 connect the left and right sides of phase change region 220. These interconnects provide electrical conductivity and facilitate connection of semiconductor device 200 as an element in a circuit with external components (not shown). Dielectric layer 235 is disposed over the top surface of phase change region 220 and provides support for metallic switch control contact 240. Similar to the operation described for the embodiment of FIG. 1, an electric field induced by a voltage connected across switch control contact 210 and switch control contact 240 can be used to control the phase of phase change region 220. This phase change region 220 then determines whether the switch is in the metallic phase or whether the switch is in the off state when in the insulator phase. Switch control contacts 240 form a sandwich configuration with phase change region 220 between them.

[0016] Figure 3 shows the Mo x W 1-x Graph 300 illustrates an exemplary change in current flow on the y-axis 305 versus the change in control potential on the x-axis 310 for semiconductor device 100 when a change in the phase of Te2 is used to control the off or on state of the semiconductor device. In this example, Mo x W 1-x x in Te2 can be 1 to 0.66.

[0017] Starting with a control voltage of 0 and increasing the voltage to 315 (approximately 0.5 to 5 volts), the current flow through each device has an increase of about 10 times, to just over 1E-08 amperes. However, if the control voltage is increased very slightly (approximately a 30 to 50 millivolt change) from the voltage at 315 to the voltage at 320, the current flow increases by more than 1000 times, to approximately 1E-05 amperes. Further increases in control voltage result in only marginal additional current, as shown.

[0018] Starting with a control voltage above the voltage at 320 and decreasing to the voltage at 325, the current flow through each device has a modest decrease in current flow, as shown in Figure 3. However, a very small further voltage decrease (about a 30-50 millivolt change) in the control voltage from the voltage at 325 to the voltage at 330 causes a thousand-fold decrease in current flow to about 1E-08 amps. Further decrease in control voltage results in a decrease in the current flow, as shown in Figure 3. This results in a ten-fold decrease in further current of 1E-09 amperes, as shown in Figure 3. It is clear that there is a hysteresis loop between the phase transition from the OFF state to the ON state and the phase transition from the ON state to the OFF state, as shown in Figure 3.

[0019] The switches or transistors described in these embodiments have a V across the switch. GS、 and I flowing through the phase change region 130 in the switch. DS It is important to understand that the FET provides a very sharp switching transition of approximately 30-50 millivolts of voltage change for every 10 times the current change. This provides a substantial improvement in the speed of switching state transitions compared to the switching transitions of conventional silicon FETs, which have switching transitions of 60 millivolts or more for every 10 times the current change. As will be appreciated by those skilled in the art, the faster switching times of the device also translate into the analog frequency domain for improved higher frequency performance, such as when the device is utilized as an analog RF amplifier.

[0020] 4, 5, and 6 show semiconductor devices 400, 500, and 600, respectively, at different steps in the manufacturing process. x W 1-x 4 illustrates cross-sectional views of semiconductor devices 400, 500, and 600 of embodiments utilizing Te2. As seen in the processing steps of FIG. 4, semiconductor device 400 includes a semiconductor channel 405 of a typical semiconductor, such as Si, GaAs, InGaAs, or GaN, disposed on a substrate 408, such as Si, GaAs, InP, sapphire, and SiC. A source region 410 and a spaced-apart drain region 415 are deposited on the top surface of semiconductor channel 405. A dielectric 420 is disposed on top of semiconductor channel 405 between source region 410 and drain region 415. A gate region 425 is deposited on top of dielectric 420, between but not engaging source region 410 and drain region 415. Source region 410, gate region 425, and drain region 415 are formed of Mo x W 1-x These are formed by depositing the alloy metals Mo and W, respectively, in accordance with the following formula: The metals may be co-deposited or a superlattice may be formed, i.e., the deposition of the combination may be repeated one after the other. The choice of "x" in the composition is a factor in controlling the magnitude of the electric field required to cause the phase change.

[0021] In an exemplary embodiment, the source region 410 is fabricated to require a lower magnitude electric field to induce the phase transition, e.g., a higher W concentration such as 0.2-0.3 with a respective x value of 0.8-0.7. The gate region 425 may be fabricated to require a higher magnitude electric field to induce the phase transition, e.g., a W concentration such as 0-0.1 with a corresponding x value of 1-0.9. The drain region 415 may be fabricated to require a higher magnitude electric field to induce the phase transition, utilizing the same ratios as described for the gate region 425.

[0022] FIG. 5 shows a semiconductor device 500 resulting from semiconductor device 400 having source region 410, gate region 425, and drain region 415 exposed to a vapor concentration of Te. The Te vapor is preferably deposited at high temperatures, between 400 and 1200°C, which determines its phase at room temperature without the application of an electric field. When the Te is fully reacted, semiconductor device 500 will have source region 510, gate region 525, and drain region 515.

[0023] 6 shows semiconductor device 600 with conventional metal layer pads 605, 610, and 615 deposited on source region 510, gate region 525, and drain region 515, respectively. These metal layer pads 605, 610, and 615 facilitate the attachment of wires, runners, or bonds to the respective terminals of semiconductor device 600 for connecting semiconductor device 600 to external circuitry. Thus, semiconductor device 600 allows the completed, fabricated device to operate in analog mode as a sharp transition digital switch or high frequency amplifier.

[0024] FIG. 7 illustrates a cross-section of a semiconductor device 700 as another embodiment of a semiconductor device according to the present invention. The semiconductor device 700 represents a conventional semiconductor FET with modifications, as will be described below. A semiconductor channel 710 is disposed on a conventional substrate 705. A conventional source region 715 and a spaced-apart drain region 720 are disposed above the semiconductor channel 710. A gate dielectric 725 is disposed between the source region 715 and the drain region 720, and a metal gate region 730 is disposed thereon between the source region 715 and the drain region 720, typically closer to the source region 715 than to the drain region 720. A layer of phase change material 735 is disposed on top of the gate dielectric 725, spaced apart between the metal gate region 730 and the drain region 720. During operation of the semiconductor device 700, changes in the electric field between the metal gate region 730 and the drain region 720 cause a change in the phase change material 735. x W 1-xA layer of phase change material 735 made of Te2 is transformed between a metal and an insulator. In the metal phase, this extended shield plate screens traps that may form between the metal gate region 730 and the drain region 720, as designated by xxx in the figure. In the insulator phase, the phase change material 735, acting as a shield plate, is no longer conducting, thereby avoiding parasitic short channel effects typically seen when using a fully metallic shield plate layer between the metal gate region 730 and the drain region 720.

[0025] FIG. 8 shows a cross-sectional view of semiconductor device 800, another embodiment of a semiconductor device according to the present invention. Semiconductor device 800 represents a conventional FET modified with other variations, as described below. A conventional substrate 805 has a semiconductor channel 810 disposed thereon. A conventional source region 815 and a spaced-apart drain region 820 are disposed above the semiconductor channel 810. A gate dielectric 825 is disposed between the source region 815 and the drain region 820, and a metal gate region 830 is disposed thereon between the source region 815 and the drain region 820, typically closer to the source region 815 than to the drain region 820. A layer of phase change material 835 is disposed on top of gate dielectric 825 closest to the drain region 820 and connected to the edge of metal gate region 830 that extends laterally toward, but does not engage, the drain region 820. A field applied between the metal gate region 830 and the drain region 820 can be utilized to turn the gate extension provided by the phase change material 835 into an on state and an off state. In the off state, the phase change material 835 acts as an insulator, limiting the effective area of ​​the metal gate region 830 to only the area occupied by the physically short metal gate region 830, providing improved high frequency response. In the on state, the phase change material 835 acts as a metal, with the gate region 830 and the phase change material 835 combined creating an effective gate. The phase change extension also acts as a shielding trap at the channel surface, improving breakdown, mitigating short channel effects, and providing a longer, effective gate.

[0026] 9 is a flow diagram illustrating steps in the fabrication of one embodiment of a FET semiconductor according to the present invention. In step 905, a conventional semiconductor FET structure is fabricated, but without the usual metal contacts deposited to facilitate connection to the device terminals. In step 910, Mo x W 1-x A layer of Mo is deposited on the source, drain, and gate regions. This phase change material may be deposited by co-deposition of Mo and W, or thin monolayers of each may be deposited alternately. The ratio of W to Mo can be controlled to establish a static phase even at room temperature without an applied electric field. Application of an appropriate electric field, e.g., via a voltage difference, to the phase change material induces a phase change from metal to insulator, or from insulator to metal. Useful ratios and corresponding X values ​​in the formula are described above. In step 915, a layer of phase change material is deposited on the exposed surface of the phase change material by exposing Te vapor at high temperature. Typically, Te deposited using temperatures between 400 and 600 degrees Celsius has an insulating state at room temperature operation, while temperatures between 650 and 1,100 degrees Celsius result in a phase change material with a metallic state at room temperature operation. In the final step 920, the source, drain, and gate regions are deposited. A layer of metal is deposited over the phase change layer to provide connecting contacts to the gate region and the gate region, respectively.

[0027] FIG. 10 shows a schematic diagram of an exemplary circuit that may be used to provide a voltage difference that generates a field sufficient to control the phase of a phase change material, as used in a FET 1005. The FET 1005 includes a drain region 1010, a gate region 1015, and a source region 1020. An additional control gate terminal 1025 is made of phase change material 735, as previously described herein. The additional control gate terminal 1025 is a schematic representation of a layer of phase change material 735 as shown in FIG. 7. Assuming the FET 1005 is in an active / on state, a DC voltage source 1030 supplies current to the drain region 1010 through a load 1035. The drain current flows through the FET's semiconductor channel, out the source region 1020 through circuit element 1040, completing the circuit to ground for the voltage source 1030. A variable DC voltage source 1045 supplies an operating gate voltage to the gate region 1015 through an isolated circuit element 1050. An AC signal source 1055 is coupled to the gate region 1015 through an isolation circuit element 1060. Depending on the gain of the FET 1005, the signal from the AC signal source 1055 appears at the drain region 1010 with an amplified magnitude.

[0028] According to one embodiment of the present invention, a variable DC voltage source 1065 is coupled to an additional control gate terminal 1025 of phase change material through an isolation circuit element 1070. The advantages of controlling the semiconducting and insulating phases of the phase change material by varying the voltage applied by voltage source 1065 are described with reference to Figures 7 and 8. DC voltage source 1065 has a voltage range sufficient to provide the predetermined phase change voltage levels required to transition the phase change material between the metallic and insulating phases.

[0029] FIG. 11 shows a schematic diagram of an exemplary circuit that may be used to provide a voltage difference that generates a field sufficient to control the phase of a phase-change material used as an on / off semiconductor switch 1100. In this exemplary embodiment, a channel 1105 is fabricated from a phase-change material as described herein. Metal contacts 1110 and 1115 are disposed at each end of the channel 1105, allowing for the attachment of connecting wires 1120 and 1125, respectively. The wires may be utilized to connect the on / off semiconductor to other external circuits (not shown) through which current flow is to be controlled by the on / off semiconductor switch 1100. Dielectric layers 1130 and 1135 are disposed on opposite lateral sides of the channel 1105. Metal pads 1140 and 1145 are disposed on the dielectric layers 1130 and 1135, respectively, forming a sandwich configuration with the channel 1105. A variable DC voltage source 1150 is connected across the metal pads 1140 and 1145, such that a DC voltage supplied by the source region 1150 generates a corresponding internal electric field induced on the lateral sides of the channel 1105. As previously described, the phase change material utilized in the channel 1105 is in one of a metallic phase and an insulating phase without a voltage applied by the source region 1150. With a voltage applied by the source region 1150 sufficient to reach a predetermined phase change voltage level, the phase change material utilized in the channel 1105 transitions to the other of a metallic phase and an insulating phase. Thus, the on / off semiconductor switch 1100 can be controllably switched as an on state when the channel 1105 is in the metallic phase and an off state when the channel 1105 is in the insulating phase. As previously described, the transition between the on / off states can be achieved in a shorter time frame than conventional switches based on silicon technology.

[0030] While illustrative embodiments of the present invention have been shown and described in detail herein, it will be apparent to those skilled in the art that various modifications, additions, substitutions, etc. may be made therein without departing from the spirit of the invention. The following are additional features of the present invention. (Additional note 1) 1. A semiconductor device comprising: a semiconductor channel having opposing first and second ends and opposing first and second lateral sides; the semiconducting channel supports current flow through the semiconducting channel from the first end to the second end while the semiconducting channel is in a metallic phase; The semiconductor channel is Mo x W 1-x Made from Te2 phase change material, The phase change material is in one of the metallic phase or the insulator phase in the absence of a voltage difference across the first lateral side and the second lateral side, and is in the other of the metallic phase or the insulator phase in the presence of an electric field due to a voltage difference across the first lateral side and the second lateral side that is greater than a phase change voltage difference, and no substantial current flows from the first end to the second end while the semiconductor channel is in the insulator phase. Semiconductor devices. (Additional note 2) functions as a switch having an on state and an off state, the on state corresponding to the phase change material being in the metallic phase and the off state corresponding to the phase change material being in the insulator phase Item 1. The semiconductor device according to item 1. (Additional note 3) a substrate supporting the semiconductor channel; a first metal pad and a second metal pad; a first dielectric material disposed on the substrate and engaging the first lateral side, the first dielectric material separating the first metal pad from the first lateral side; a second dielectric material disposed on the second lateral side and separating the second metal pad from the second lateral side; The first metal pad and the second metal pad form a sandwich configuration with the semiconductor channel, facilitating application of a field across the semiconductor channel when a voltage difference is established on the first metal pad relative to the second metal pad. Item 1. The semiconductor device according to item 1. (Additional note 4) the transition between the on state and the off state, corresponding to the transition between the metallic phase and the insulator phase, proceeds at a rate that increases current by a factor of 10 or more for every 60 millivolts of voltage difference across the semiconductor channel. Item 2. The semiconductor device according to claim 2. (Additional note 5) The transition between the on state and the off state proceeds in such a way that the change in current for each unit change in voltage difference across the semiconductor channel is greater than that of a FET that does not use the phase change material. Item 5. The semiconductor device according to item 4. (Additional note 6) The phase change material changes from one of the metallic phase and the insulator phase to the other of the metallic phase and the insulator phase while the semiconductor channel remains substantially at room temperature. Item 1. The semiconductor device according to item 1. (Additional note 7) a semiconductor channel; spaced apart source and drain regions disposed on a surface of the semiconductor channel; a dielectric layer disposed on the surface of the semiconductor channel between the source region and the drain region; a gate region disposed on a surface of the dielectric layer opposite the surface of the semiconductor channel and disposed between the source region and the drain region; The source region, the gate region, and the drain region are each made of Mo x W 1-x including a Te2 phase change material, and metal contacts disposed on the source region, the gate region, and the drain region, respectively, to facilitate electrical connection with the source region, the gate region, and the drain region. Field effect transistor. (Additional note 8) In the material composition formula, x is a positive number less than or equal to 1.0, and the value of x is different for the materials used in the source region and the gate region, and the source region has a lower x value than the x value for the gate region. Item 8. The field-effect transistor according to item 7. (Additional note 9) The value of x in the material composition formula of each region is In the source region, 0.7 <x<0.8、 In the gate area, 0.9 <x<1.0、 In the drain region, 0.9 <x<1.0 9. The field-effect transistor according to claim 8, wherein (Additional note 10) The phase change material is changed at room temperature from one of a metallic phase and an insulator phase to another of the metallic phase and the insulator phase depending on whether a voltage difference greater than a predetermined phase change voltage exists across the phase change material. Item 8. The field-effect transistor according to item 7. (Additional note 11) a semiconductor channel; spaced apart source and drain regions disposed on a surface of the semiconductor channel; a dielectric layer disposed on a surface of the semiconductor channel between the source region and the drain region; a gate region disposed on a surface of the dielectric layer opposite the surface of the semiconductor channel and disposed between the source region and the drain region; the source region, the gate region, and the drain region are each metal regions; a control region disposed on a surface of the dielectric layer between the gate region and the drain region, the control region having a semiconducting phase and an insulating phase depending on whether a control voltage field is present across the control region; x W 1-x a control region comprising a Te2 phase change material, the control region of the semiconducting phase functions to passivate traps at a surface of the semiconducting channel between the gate region and the drain region; the control region of the insulator phase does not present a physically active region adjacent to the gate region, thereby improving the high frequency response of the field effect transistor; Field effect transistor. (Additional note 12) In the material composition formula, x is a positive number equal to or less than 1.0, and the value of x is between 0.1 and 0.9. Item 12. The field effect transistor according to item 11. (Additional note 13) The gate region and the control region are not in contact with each other but are spaced apart. Item 12. The field effect transistor according to item 11. (Additional note 14) The gate region and the control region abut against each other and are electrically connected to each other. Item 12. The field effect transistor according to item 11. (Additional note 15) The phase change material changes from one of a metallic phase and an insulator phase to another of the metallic phase and an insulator phase at room temperature depending on whether a voltage difference is present across the phase change material. Item 12. The field effect transistor according to item 11.

[0031] The scope of the present invention is defined in the following claims.

Claims

1. a semiconductor channel; spaced apart source and drain regions disposed on a surface of the semiconductor channel; a dielectric layer disposed on the surface of the semiconductor channel between the source region and the drain region; a gate region disposed on a surface of the dielectric layer opposite the surface of the semiconductor channel and disposed between the source region and the drain region; The source region, the gate region, and the drain region are each made of Mo ｘ W １－ｘ Te ２ a phase change material of and metal contacts disposed on the source region, the gate region, and the drain region, respectively, to facilitate electrical connection with the source region, the gate region, and the drain region. Field effect transistor.

2. In the material composition formula, x is a positive number less than or equal to 1.0, and the value of x is different for the materials used in the source region and the gate region, and the source region has a lower x value than the x value for the gate region.

2. The field effect transistor of claim 1.

3. The value of x in the material composition formula of each region is In the source region, 0.7<x<0.8; In the gate region, 0.9<x<1.0, In the drain region, 0.9<x<1.0 3. The field effect transistor according to claim 2, wherein

4. The phase change material is changed at room temperature from one of a metallic phase and an insulator phase to another of the metallic phase and the insulator phase depending on whether a voltage difference greater than a predetermined phase change voltage exists across the phase change material.

2. The field effect transistor of claim 1.

5. a semiconductor channel; spaced apart source and drain regions disposed on a surface of the semiconductor channel; a dielectric layer disposed on a surface of the semiconductor channel between the source region and the drain region; a gate region disposed on a surface of the dielectric layer opposite the surface of the semiconductor channel and disposed between the source region and the drain region; the source region, the gate region, and the drain region are each metal regions; a control region disposed on a surface of the dielectric layer between the gate region and the drain region, the control region having a semiconducting phase and an insulating phase depending on whether a control voltage field is present across the control region; ｘ W １－ｘ Te ２ a control region comprising a phase change material, the control region of the semiconductor phase functions to passivate traps at a surface of the semiconductor channel between the gate region and the drain region; the control region of the insulator phase does not present a physically active region adjacent to the gate region, thereby improving the high frequency response of the field effect transistor. Field effect transistor.

6. In the material composition formula, x is a positive number of 1.0 or less, and the value of x is between 0.1 and 0.

9.

6. The field effect transistor of claim 5.

7. The gate region and the control region are not in contact with each other but are spaced apart.

6. The field effect transistor of claim 5.

8. The gate region and the control region abut against each other and are electrically connected to each other.

6. The field effect transistor of claim 5.

9. The phase change material changes from one of a metallic phase and an insulator phase to another of the metallic phase and an insulator phase at room temperature depending on whether a voltage difference is present across the phase change material.

6. The field effect transistor of claim 5.

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