1. A tunneling field effect transistor, comprising a semiconductor substrate (1), a channel region (6), a highly-doped source region (3), a lightly-doped drain region (4), a gate dielectric layer (7), and a control gate (8),
wherein the channel region (6) is in a cuboid shape; when viewing from a horizontal direction, a side of the channel region (6) extends into the highly-doped source region (3), and the other side thereof is connected to the lightly-doped drain region (4); when viewing from a vertical direction, the channel region (6) is located under the control gate (8) and the gate dielectric layer (7); the channel region (6) extending into the highly-doped source region (3) is surrounded at three sides by the highly-doped source region (3), while the channel region (6) not extending into the highly-doped source region (3) is surrounded by the semiconductor substrate (1); the control gate (8) is spaced apart from the lightly-doped drain region (4) by a horizontal interval; the control gate (8) covers the highly-doped source region (3) and a part of the channel region (6); the lightly-doped drain region (4) and the highly-doped source region (3) are doped with different types of impurities; the lightly-doped drain region (4) has a doping concentration between 5\xd71017 cm\u22123 and 1\xd71019 cm\u22123, and the highly-doped source region (3) has a doping concentration between 1\xd71019 cm\u22123 and 1\xd71021 cm\u22123.
2. The tunneling field effect transistor according to claim 1, wherein both of the semiconductor substrate (1) and the channel region (6) have a doping concentration between 1\xd71014 cm\u22123 and 1\xd71017 cm\u22123.
3. The tunneling field effect transistor according to claim 1, wherein the cuboid shaped channel region (6) has equal width and height, which is less than twice width of a source depletion layer, the width of the source depletion layer having a range between 25 nm and 1.5 \u03bcm; the channel region (6) has a length greater than a width and a height, a ratio of the length to the width and height of the channel region (6) being between 1.5:1 and 5:1.
4. The tunneling field effect transistor according to claim 1, wherein the horizontal interval between the lightly-doped drain region (4) and the control gate (8) is between 10 nm and 1 \u03bcm.
5. A fabrication method of the tunneling field effect transistor according to claim 1, comprising the steps of:
step 1: defining an active region on a semiconductor substrate by a shallow trench isolation process;
step 2: exposing a source doping region by photolithography, and forming a highly-doped source region by performing ion implantation using a photoresist as a mask;
step 3: exposing a drain doping region by photolithography, forming a lightly-doped drain region having a different doping type by performing ion implantation using a photoresist as a mask, and then performing annealing to activate the doped impurities;
step 4: depositing a hard mask material, and then performing photolithography and etching on the hard mask material to form a horizontal pattern exposing a location of the channel region, the pattern incorporating a part of the highly-doped region and a part of the semiconductor substrate;
step 5: forming a cuboid region where the channel region is located by etching under protection of the hard mask material;
step 6: performing selective epitaxy to epitaxially grow a lightly-doped channel region under protection of the hard mask material, and performing chemical mechanical planarization using the hard mask material as a stop layer;
step 7: etching a certain thickness of the epitaxial material under protection of the hard mask material, the thickness being consistent with a thickness of the hard mask material; removing the hard mask material by using etching; and reducing surface roughness using sacrificial oxidation or hydrogen annealing;
step 8: growing a gate dielectric layer and depositing a control gate material; performing photolithography and etching to form a control gate pattern, the control gate being spaced apart from the lightly-doped drain region by a certain interval;
step 9: proceeding to conventional CMOS back-end processes to fabricate the tunneling field effect transistor according to claim 1.
6. The fabrication method according to claim 5, wherein material of the semiconductor substrate in the step 1 is selected from Si, Ge, SiGe, GaAs or other binary or ternary compound semiconductor of Groups II-VI, III-V and IV-IV, or silicon on insulator or germanium on insulator.
7. The fabrication method according to claim 5, wherein material of the epitaxially grown channel region in the step 6 is selected from Si, Ge, SiGe, GaAs or other binary or ternary compound semiconductor of Groups II-VI, III-V and IV-IV.
8. The fabrication method according to claim 5, wherein material of the gate dielectric layer in the step 8 is selected from SiO2, Si3N4, and high-K gate dielectric.
9. The fabrication method according to claim 5, wherein the control gate material in the step 9 is selected from doped polysilicon, metal cobalt, nickel and other metal or metal silicide.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method comprising:
selecting, at a wireless communication device, one of a plurality of time intervals in a periodically repeating access cycle for transmission of an access signal, the selection being performed based on an identification number identifying the wireless communication device;
negotiating, at the wireless communication device, a preamble assignment for the selected one of the plurality of time intervals; and
transmitting, at the wireless communication device, the access signal over an access channel in the selected one of the plurality of time intervals using a preamble corresponding to the preamble assignment.
2. The method of claim 1 wherein negotiating the preamble comprises:
requesting the preamble assignment for the selected one of the plurality of time intervals from a network node; and
receiving the preamble assignment for the selected one of the plurality of time intervals from the network node.
3. The method of claim 1 wherein the preamble assignment for the selected one of the plurality of time intervals is unique to the wireless communication device.
4. The method of claim 1 further comprises:
receiving a blocking signal indicating at least a first time interval of the plurality of time intervals in which access should be prevented; and
blocking transmission of the access signal over an access channel in the selected one of the plurality of time intervals using a preamble corresponding to the preamble assignment based on the blocking signal.
5. The method of claim 1 further comprising defining the plurality of time intervals in the access cycle based on synchronization information broadcast over an air interface to the wireless communication device so that the wireless communication device is synchronized with other wireless communication devices on the same access cycle with the same numbering of the time intervals.
6. The method of claim 5 wherein the plurality of time intervals are a plurality of time slots in the periodically repeating access cycle, and wherein selecting one of the plurality of time intervals comprises selecting one of the plurality of time slots based on a slot numbering comprising system frame number associated with the selected one of the slots and broadcast over the air interface.
7. The method of claim 6 wherein selecting one of the plurality of time slots comprises selecting a time slot associated with a system frame number when the system frame number is equal to the identification number modulo a period of the access cycle.
8. The method of claim 6 wherein selecting one of the plurality of time slots comprises selecting a time slot associated with a system frame number when the system frame number is equal to a selected portion or permutation of the identification number.
9. The method of claim 6 wherein selecting one of the plurality of time slots comprises selecting a time slot associated with a system frame number when the system frame number is equal to a hash of the identification number.
10. The method of claim 1 wherein a period of the access cycle is equal to a period of a paging cycle for the wireless communication device, and wherein selecting said one of the plurality of time intervals for the access signal comprises selecting a time interval immediately following a time interval assigned for paging the wireless communication device.
11. The method of claim 1 wherein selecting said one of the plurality of time intervals comprises selecting one of the plurality of time intervals in an access cycle determined by a reporting interval for the wireless communication device.