US6548842B1 — Field-effect transistor for alleviating short-cha…

Claim 1

Independent Claim 185 words

A structure comprising a principal field-effect transistor comprising: a channel zone of body material of a semiconductor body having an upper surface, the body material being of a first conductivity type; a pair of source/drain zones situated in the semiconductor body along its upper surface, laterally separated by the channel zone, and being of a second conductivity type opposite to the first conductivity type so as to form respective pn junctions with the body material, the channel zone having a net dopant concentration that longitudinally reaches a local surface minimum along the body's upper surface at a location between the source/drain zones, a channel surface depletion region extending along the body's upper surface into the channel zone, the body material having a net dopant concentration that reaches a primary local subsurface maximum below the channel surface depletion region, the primary local subsurface maximum occurring more than 0.1 μm below the body's upper surface but not more than 0.4 μm below the body's upper surface; a gate dielectric layer overlying the channel zone; and a gate electrode overlying the gate dielectric layer above the channel zone.

Claim 2

Dependent Claim 185 words

A structure comprising a principal field-effect transistor comprising: a channel zone of body material of a semiconductor body having an upper surface, the body material being of a first conductivity type; a pair of source/drain zones situated in the semiconductor body along its upper surface, laterally separated by the channel zone, and being of a second conductivity type opposite to the first conductivity type so as to form respective pn junctions with the body material, the channel zone having a net dopant concentration that longitudinally reaches a local surface minimum along the body's upper surface at a location between the source/drain zones, a channel surface depletion region extending along the body's upper surface into the channel zone, the body material having a net dopant concentration that reaches a primary local subsurface maximum below the channel surface depletion region, the primary local subsurface maximum occurring more than 0.1 μm below the body's upper surface but not more than 0.4 μm below the body's upper surface; a gate dielectric layer overlying the channel zone; and a gate electrode overlying the gate dielectric layer above the channel zone.

Claim 3

Dependent Claim 55 words

A structure as in claim 1 wherein the channel zone's net dopant concentration is of an average value that increases with decreasing length of the channel zone when a given amount of semiconductor dopant per unit width of the channel zone causes the channel zone's net dopant concentration to vary along the body's upper surface.

Claim 4

Dependent Claim 48 words

A structure as in claim 1 wherein, relative to the location of the local surface minimum of the channel zone's net dopant concentration, the channel zone's net dopant concentration along the body's upper surface is greater than the local surface minimum at locations closer to both source/drain zones.

Claim 5

Dependent Claim 33 words

A structure as in claim 3 wherein the channel zone's net dopant concentration increases in moving along the body's upper surface from the location of the local surface minimum towards each source/drain zone.

Claim 6

Dependent Claim 39 words

A structure as in claim 4 wherein the local surface minimum in the channel zone's net dopant concentration occurs approximately at a single point along an imaginary line extending longitudinally between the source/drain zones along the body's upper surface.

Claim 7

Dependent Claim 40 words

A structure as in claim 4 wherein the channel zone's net dopant concentration is approximately constant at the local surface minimum along a non-zero portion of an imaginary line extending longitudinally between the source/drain zones along the body's upper surface.

Claim 8

Dependent Claim 64 words

A structure as in claim 3 wherein the local surface minimum of the channel zone's net dopant concentration increases in value with decreasing length of the channel zone when a given amount of semiconductor dopant per unit width of the channel zone causes the channel zone's net dopant concentration to vary along the body's upper surface and when the channel zone is sufficiently short.

Claim 9

Dependent Claim 31 words

A structure as in claim 1 wherein the body material's net dopant concentration reaches a further local subsurface maximum deeper below the body's upper surface than the primary local subsurface maximum.

Claim 10

Dependent Claim 29 words

A structure as in claim 8 wherein the further local subsurface maximum of the body material's net dopant concentration occurs at least 0.4 μm below the body's upper surface.

Claim 11

Dependent Claim 30 words

A structure as in claim 9 wherein the further local subsurface maximum of the body material's net dopant concentration occurs no more than 0.7 μm below the body's upper surface.

Claim 12

Dependent Claim 23 words

A structure as in claim 8 wherein the channel surface depletion region extends to less than 0.1 μm below the body's upper surface.

Claim 13

Dependent Claim 29 words

A structure as in claim 8 wherein the primary local subsurface maximum of the body material's net dopant concentration occurs at least 0.15 μm below the body's upper surface.

Claim 14

Dependent Claim 30 words

A structure as in claim 12 wherein the primary local subsurface maximum of the body material's net dopant concentration occurs no more than 0.35 μm below the body's upper surface.

Claim 15

Dependent Claim 29 words

A structure as in claim 12 herein the further local subsurface maximum of the body material's net dopant concentration occurs at least 0.4 μm below the body's upper surface.

Claim 16

Dependent Claim 30 words

A structure as in claim 14 wherein the further local subsurface maximum of the body material's net dopant concentration occurs no more than 0.7 μm below the body's upper surface.

Claim 17

Dependent Claim 46 words

A structure as in claim 8 wherein the body material's net dopant concentration reaches a tertiary local subsurface maximum deeper below the body's upper surface than the primary local subsurface maximum but not as deep below the body's upper surface as the further local subsurface maximum.

Claim 18

Dependent Claim 29 words

A structure as in claim 16 wherein the tertiary local subsurface maximum of the body material's net dopant concentration occurs at least 0.3 μm below the body's upper surface.

Claim 19

Dependent Claim 30 words

A structure as in claim 17 wherein the tertiary local subsurface maximum of the body material's net dopant concentration occurs no more than 0.5 μm below the body's upper surface.

Claim 20

Dependent Claim 23 words

A structure as in claim 16 wherein the channel surface depletion region extends to less than 0.1 μm below the body's upper surface.

Claim 21

Dependent Claim 27 words

A structure as in claim 16 wherein the primary local subsurface maximum of the body material's net dopant concentration occurs 0.15-0.35 μm below the body's upper surface.

Claim 22

Dependent Claim 27 words

A structure as in claim 20 wherein the further local subsurface maximum of the body material's net dopant concentration occurs 0.4-0.7 μm below the body's upper surface.

Claim 23

Dependent Claim 27 words

A structure as in claim 21 wherein the tertiary local subsurface maximum of the body material's net dopant concentration occurs 0.3-0.5 μm below the body's upper surface.

Claim 24

Dependent Claim 29 words

A structure as in claim 1 wherein the primary local subsurface maximum of the body material's net dopant concentration occurs at least 0.15 μm below the body's upper surface.

Claim 25

Dependent Claim 30 words

A structure as in claim 23 wherein the primary local subsurface maximum of the body material's net dopant concentration occurs no more than 0.35 μm below the body's upper surface.

Claim 26

Dependent Claim 23 words

A structure as in claim 1 wherein the channel surface depletion region extends to less than 0.1 μm below the body's upper surface.

Claim 27

Dependent Claim 17 words

A structure as in claim 1 wherein the gate dielectric layer has a thickness of 2-10 nm.

Claim 28

Dependent Claim 20 words

A structure as in claim 26 wherein the gate dielectric layer comprises atoms of semiconductor material and atoms of oxygen.

Claim 29

Dependent Claim 12 words

A structure as in claim 27 wherein the semiconductor material comprises silicon.

Claim 30

Dependent Claim 17 words

A structure as in claim 27 wherein the gate dielectric layer has a thickness of 3-5 nm.

Claim 31

Dependent Claim 16 words

A structure as in claim 27 wherein the gate dielectric layer further includes atoms of nitrogen.

Claim 32

Dependent Claim 12 words

A structure as in claim 30 wherein the semiconductor material comprises silicon.

Claim 33

Dependent Claim 42 words

A structure as in claim 1 wherein each source/drain zone comprises a main source/drain portion and a more lightly doped source/drain extension laterally continuous with the main drain portion, the channel zone being terminated by the extensions along the body's upper surface.

Claim 34

Dependent Claim 36 words

A structure as in claim 1 wherein the transistor has a threshold voltage that varies with the depth, below the body's upper surface, of the primary local subsurface maximum of the body material's net dopant concentration.

Claim 35

Dependent Claim 45 words

A structure as in claim 1 wherein: the channel zone has a channel length; and the channel zone's net dopant concentration is of an average value which, at a given set of fabrication process conditions for the transistor, generally increases as the channel length decreases.

Claim 36

Dependent Claim 52 words

A structure as in claim 34 wherein: the transistor has a threshold voltage; and decreasing the channel length to increase the average value of the channel zone's net dopant concentration enables the threshold voltage to reach a maximum absolute value V TAM at a certain value L C of the channel length.

Claim 37

Dependent Claim 34 words

A structure as in claim 35 wherein the threshold voltage is, in absolute value, at least 0.03 volt less than V TAM when the channel length is 0.3 μm greater than L C .

Claim 38

Dependent Claim 34 words

A structure as in claim 36 wherein the threshold voltage is, in absolute value, at least 0.1 volt less than V TAM when the channel length is 1.0 μm greater than L C .

Claim 39

Dependent Claim 213 words

A structure as in claim 1 further including an additional field-effect transistor of like polarity to the principal transistor, the additional transistor comprising: an additional channel zone of the body material; a pair of additional source/drain zones situated in the semiconductor body along its upper surface, laterally separated by the additional channel zone, and being of the second conductivity type so as to form respective additional pn junctions with the body material, the additional channel zone having a net dopant concentration that longitudinally reaches an additional local surface minimum along the body's upper surface at a location between the additional source/drain zones, an additional channel surface depletion region extending along the body's upper surface into the additional channel zone, the body material's net dopant concentration reaching an additional primary local subsurface maximum below the additional channel surface depletion region, the additional primary local subsurface maximum occurring more than 0.1 μm below the body's upper surface but not more than 0.4 μm below the body's upper surface; an additional gate dielectric layer overlying the additional channel zone; and an additional gate electrode overlying the additional gate dielectric layer above the additional channel zone, the channel zones of the two transistors being of sufficiently different channel length that the transistors differ significantly in threshold voltage.

Claim 40

Dependent Claim 45 words

A structure as in claim 38 wherein the net dopant concentrations of the channel zones have respective surface variations that respectively include the local surface minima, the surface variations being caused by approximately equal amounts of semiconductor dopant per unit width of the channel zones.

Claim 41

Dependent Claim 27 words

A structure as in claim 39 wherein the channel zone of shorter channel length is of significantly higher average net dopant concentration than the other channel zone.

Claim 42

Dependent Claim 29 words

A structure as in claim 38 wherein the transistor with the channel zone of shorter channel length is, in absolute value, of greater threshold voltage than the other transistor.

Claim 43

Dependent Claim 33 words

A structure as in claim 38 wherein the local surface minima of the channel zones' net dopant concentrations differ significantly in absolute value under largely identical fabrication process conditions for the two transistors.

Claim 44

Dependent Claim 40 words

A structure as in claim 38 wherein the transistor with the channel zone of shorter channel length has the local surface minimum of greater value so as to be, in absolute value, of greater threshold voltage than the other transistor.

Claim 45

Dependent Claim 42 words

A structure as in claim 38 wherein the net dopant concentration of each channel zone along the body's upper surface is significantly greater than that channel zone's local surface minimum at locations closer to both source/drain zones which bound that channel zone.

Claim 46

Dependent Claim 35 words

A structure as in claim 38 wherein the body material's net dopant concentration reaches a further local subsurface maximum deeper below the body's upper surface than each of the body material's primary local subsurface maxima.

Claim 47

Dependent Claim 42 words

A structure as in claim 38 wherein the body material comprises a pair of body regions laterally separated by semiconductor material of opposite conductivity type to the body material, each channel zone being situated in a different one of the body regions.

Claim 48

Dependent Claim 29 words

A structure as in claim 38 wherein each primary local subsurface maximum of the body material's net dopant concentration occurs at least 0.15 μm below the body's upper surface.

Claim 49

Dependent Claim 30 words

A structure as in claim 47 wherein each primary local subsurface maximum of the body material's net dopant concentration occurs no more than 0.35 μm below the body's upper surface.

Claim 50

Dependent Claim 23 words

A structure as in claim 38 wherein each channel surface depletion region extends to less than 0.1 μm below the body's upper surface.

Claim 51

Dependent Claim 37 words

A structure as in claim 38 wherein the body material's net dopant concentration reaches, for each transistor, a further local subsurface maximum deeper below the body's upper surface than the primary local subsurface maximum for that transistor.

Claim 52

Dependent Claim 27 words

A structure as in claim 50 wherein each further local subsurface maximum of the body material's net dopant concentration occurs 0.4-0.7 μm below the body's upper surface.

Claim 53

Dependent Claim 23 words

A structure as in claim 50 wherein each channel surface depletion region extends to less than 0.1 μm below the body's upper surface.

Claim 54

Dependent Claim 27 words

A structure as in claim 50 wherein each primary local subsurface maximum of the body material's net dopant concentration occurs 0.15-0.35 μm below the body's upper surface.

Claim 55

Dependent Claim 27 words

A structure as in claim 50 wherein each further local subsurface maximum of the body material's net dopant concentration occurs 0.4-0.7 μm below the body's upper surface.

Claim 56

Dependent Claim 55 words

A structure as in claim 50 wherein the body material's net dopant concentration reaches, for each transistor, a tertiary local subsurface maximum deeper below the body's upper surface than the primary local subsurface maximum for that transistor but not as deep below the body's upper surface as the further local subsurface maximum for that transistor.

Claim 57

Dependent Claim 29 words

A structure as in claim 50 wherein each tertiary local subsurface maximum of the body material's net dopant concentration occurs at least 0.3 μm below the body's upper surface.

Claim 58

Dependent Claim 23 words

A structure as in claim 55 wherein each channel surface depletion region extends to less than 0.1 μm below the body's upper surface.

Claim 59

Dependent Claim 27 words

A structure as in claim 55 wherein each primary local subsurface maximum of the body material's net dopant concentration occurs 0.15-0.35 μm below the body's upper surface.

Claim 60

Dependent Claim 27 words

A structure as in claim 58 wherein each further local subsurface maximum of the body material's net dopant concentration occurs 0.4-0.7 μm below the body's upper surface.

Claim 61

Dependent Claim 27 words

A structure as in claim 59 wherein each tertiary local subsurface maximum of the body material's net dopant concentration occurs 0.3-0.5 μm below the body's upper surface.

Claim 62

Dependent Claim 184 words

A structure comprising a pair of like-polarity field-effect transistors provided along an upper surface of a semiconductor body having body material of a first conductivity type, each transistor comprising: a channel zone of the body material; a pair of source/drain zones situated in the semiconductor body along its upper surface, laterally separated by the channel zone, and being of a second conductivity type opposite to the first conductivity type so as to form respective pn junctions with the body material, the channel zone having a net dopant concentration that longitudinally reaches a local surface minimum along the body's upper surface at a location between the source/drain zones, the body material having a net dopant concentration that reaches a primary local subsurface maximum more than 0.1 μm below the body's upper surface but not more than 0.4 μm below the body's upper surface; a gate dielectric layer overlying the channel zone; and a gate electrode overlying the gate dielectric layer above the channel zone, the channel zones of the two transistors being of sufficiently different channel length that the transistors differ significantly in threshold voltage.

Claim 63

Dependent Claim 184 words

A structure comprising a pair of like-polarity field-effect transistors provided along an upper surface of a semiconductor body having body material of a first conductivity type, each transistor comprising: a channel zone of the body material; a pair of source/drain zones situated in the semiconductor body along its upper surface, laterally separated by the channel zone, and being of a second conductivity type opposite to the first conductivity type so as to form respective pn junctions with the body material, the channel zone having a net dopant concentration that longitudinally reaches a local surface minimum along the body's upper surface at a location between the source/drain zones, the body material having a net dopant concentration that reaches a primary local subsurface maximum more than 0.1 μm below the body's upper surface but not more than 0.4 μm below the body's upper surface; a gate dielectric layer overlying the channel zone; and a gate electrode overlying the gate dielectric layer above the channel zone, the channel zones of the two transistors being of sufficiently different channel length that the transistors differ significantly in threshold voltage.

Claim 64

Dependent Claim 29 words

A structure as in claim 61 wherein the transistor with the channel zone of shorter channel length is, in absolute value, of greater threshold voltage than the other transistor.

Claim 65

Dependent Claim 33 words

A structure as in claim 61 wherein the net dopant concentrations of the channel zones are of respective average values that differ significantly under largely identical fabrication process conditions for the two transistors.

Claim 66

Dependent Claim 46 words

A structure as in claim 61 wherein the transistor having the channel zone of shorter channel length has the greater of the average values of the channel zones' net dopant concentration so as to be, in absolute value, of greater threshold voltage than the other transistor.

Claim 67

Dependent Claim 53 words

A structure as in claim 61 wherein the net dopant concentration of at least one of the channel zones increases in moving along the body's upper surface from the location of the local surface minimum of the net dopant concentration of that channel zone towards both source/drain zones which bound that channel zone.

Claim 68

Dependent Claim 35 words

A structure as in claim 61 wherein the body material's net dopant concentration reaches a further local subsurface maximum deeper below the body's upper surface than each of the body material's primary local subsurface maxima.

Claim 69

Dependent Claim 29 words

A structure as in claim 61 wherein each primary local subsurface maximum of the body material's net dopant concentration occurs at least 0.15 μm below the body's upper surface.

Claim 70

Dependent Claim 30 words

A structure as in claim 67 wherein each primary local subsurface maximum of the body material's net dopant concentration occurs no more than 0.35 μm below the body's upper surface.

Claim 71

Dependent Claim 23 words

A structure as in claim 61 wherein each channel surface depletion region extends to less than 0.1 μm below the body's upper surface.

Claim 72

Dependent Claim 37 words

A structure as in claim 61 wherein the body material's net dopant concentration reaches, for each transistor, a further local subsurface maximum deeper below the body's upper surface than the primary local subsurface maximum for that transistor.

Claim 73

Dependent Claim 29 words

A structure as in claim 70 wherein each further local subsurface maximum of the body material's net dopant concentration occurs at least 0.4 μm below the body's upper surface.

Claim 74

Dependent Claim 30 words

A structure as in claim 71 wherein each further local subsurface maximum of the body material's net dopant concentration occurs no more than 0.7 μm below the body's upper surface.

Claim 75

Dependent Claim 23 words

A structure as in claim 70 wherein each channel surface depletion region extends to less than 0.1 μm below the body's upper surface.

Claim 76

Dependent Claim 27 words

A structure as in claim 70 wherein each primary local subsurface maximum of the body material's net dopant concentration occurs 0.15-0.35 μm below the body's upper surface.

Claim 77

Dependent Claim 27 words

A structure as in claim 74 wherein each further local subsurface maximum of the body material's net dopant concentration occurs 0.4-0.7 μm below the body's upper surface.

Claim 78

Dependent Claim 55 words

A structure as in claim 70 wherein the body material's net dopant concentration reaches, for each transistor, a tertiary local subsurface maximum deeper below the body's upper surface than the primary local subsurface maximum for that transistor but not as deep below the body's upper surface as the further local subsurface maximum for that transistor.

Claim 79

Dependent Claim 29 words

A structure as in claim 76 wherein each tertiary local subsurface maximum of the body material's net dopant concentration occurs at least 0.3 μm below the body's upper surface.

Claim 80

Dependent Claim 30 words

A structure as in claim 77 wherein each tertiary local subsurface maximum of the body material's net dopant concentration occurs no more than 0.5 μm below the body's upper surface.

Claim 81

Dependent Claim 23 words

A structure as in claim 76 wherein each channel surface depletion region extends to less than 0.1 μm below the body's upper surface.

Claim 82

Dependent Claim 27 words

A structure as in claim 76 wherein each primary local subsurface maximum of the body material's net dopant concentration occurs 0.15-0.35 μm below the body's upper surface.

Claim 83

Dependent Claim 27 words

A structure as in claim 80 wherein each further local subsurface maximum of the body material's net dopant concentration occurs 0.4-0.7 μm below the body's upper surface.

Claim 84

Dependent Claim 27 words

A structure as in claim 81 wherein each tertiary local subsurface maximum of the body material's net dopant concentration occurs 0.3-0.5 μm below the body's upper surface.

Claim 85

Dependent Claim 164 words

A structure comprising a pair of like-polarity field-effect transistors provided along an upper surface of a semiconductor body having body material, each transistor comprising: a channel zone of the body material; a pair of source/drain zones situated in the semiconductor body along its upper surface, laterally separated by the channel zone, and forming respective pn junctions with the body material, the channel zone having a net dopant concentration that longitudinally reaches a local surface minimum along the body's upper surface at a location between the source/drain zones, the body material having a net dopant concentration that reaches a primary local subsurface maximum more than 0.1 μm below the body's upper surface but not more than 0.4 μm below the body's upper surface; a gate dielectric layer overlying the channel zone; and a gate electrode overlying the gate dielectric layer above the channel zone, the channel zones of the two transistors being of sufficiently different channel length that the transistors differ significantly in threshold voltage.

Claim 86

Dependent Claim 164 words

A structure comprising a pair of like-polarity field-effect transistors provided along an upper surface of a semiconductor body having body material, each transistor comprising: a channel zone of the body material; a pair of source/drain zones situated in the semiconductor body along its upper surface, laterally separated by the channel zone, and forming respective pn junctions with the body material, the channel zone having a net dopant concentration that longitudinally reaches a local surface minimum along the body's upper surface at a location between the source/drain zones, the body material having a net dopant concentration that reaches a primary local subsurface maximum more than 0.1 μm below the body's upper surface but not more than 0.4 μm below the body's upper surface; a gate dielectric layer overlying the channel zone; and a gate electrode overlying the gate dielectric layer above the channel zone, the channel zones of the two transistors being of sufficiently different channel length that the transistors differ significantly in threshold voltage.

Claim 87

Dependent Claim 29 words

A structure as in claim 83 wherein the transistor with the channel zone of shorter channel length is, in absolute value, of greater threshold voltage than the other transistor.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2006-04-14	2006-10-14	2007-04-15	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2010-04-14	2010-10-14	2011-04-15	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2014-04-14	2014-10-14	2015-04-15	$7700.00	Window Closed / Lapsed

Field-effect transistor for alleviating short-channel effects

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