EP0402296A1 — Field-effect-transistor with asymmetrical structu…

Claim 1

Independent Claim 69 words

A field effect transistor of asymmetrical structure comprising : a semiconductor substrate of first conductivity type; source and drain regions of second conductivity type disposed in a surface of said substrate and spaced apart by a channel region; and a single, lightly doped extension of said drain region into said channel, said extension being of said second conductivity type and of a lower dopant concentration than said drain region.

Claim 2

Dependent Claim 69 words

A field effect transistor of asymmetrical structure comprising : a semiconductor substrate of first conductivity type; source and drain regions of second conductivity type disposed in a surface of said substrate and spaced apart by a channel region; and a single, lightly doped extension of said drain region into said channel, said extension being of said second conductivity type and of a lower dopant concentration than said drain region.

Claim 3

Dependent Claim 17 words

The field effect transistor of claim 1 wherein said extension is proximate said surface of said substrate.

Claim 4

Dependent Claim 26 words

The field effect transistor of claim 2 and further including a gate electrode overlying said channel region and insulated from the surface of said channel region.

Claim 5

Dependent Claim 98 words

A field effect transistor of asymmetrical structure comprising : a semiconductor substrate of first conductivity type; source and drain regions of second conductivity type disposed in a surface of said substrate and spaced apart by a channel region; a single halo region generally surrounding said source region in said substrate, said halo region of said first conductivity type and of a higher doping concentration than said substrate; and a single lightly doped extension of said drain region into said channel, said extension being of said second conductivity type and of a lower dopant concentration than said drain region.

Claim 6

Dependent Claim 98 words

A field effect transistor of asymmetrical structure comprising : a semiconductor substrate of first conductivity type; source and drain regions of second conductivity type disposed in a surface of said substrate and spaced apart by a channel region; a single halo region generally surrounding said source region in said substrate, said halo region of said first conductivity type and of a higher doping concentration than said substrate; and a single lightly doped extension of said drain region into said channel, said extension being of said second conductivity type and of a lower dopant concentration than said drain region.

Claim 7

Dependent Claim 19 words

A field effect transistor in accordance with claim 4 wherein said extension is proximate said surface of said substrate.

Claim 8

Dependent Claim 24 words

A field effect transistor in accordance with claim 5 wherein said extension is of a shallower depth into said substrate than said drain region.

Claim 9

Dependent Claim 26 words

A field effect transistor in accordance with claim 4 and further including a gate electrode situated over said channel region and insulated from said channel region.

Claim 10

Dependent Claim 29 words

A field effect transistor in accordance with claim 7 wherein said gate electrode generally spans said channel to overlap said drain extension, said halo region, and said source region.

Claim 11

Independent Claim 75 words

A method of forming a field effect transistor, comprising the steps of : providing a semiconductor substrate of first conductivity type; forming source and drain regions of second conductivity type in a surface of said substrate and spaced apart by a channel region; and forming a single, lightly doped extension of said drain region into said channel, said extension being of said second conductivity type and of a lower dopant concentration than said drain region.

Claim 12

Independent Claim 75 words

A method of forming a field effect transistor, comprising the steps of : providing a semiconductor substrate of first conductivity type; forming source and drain regions of second conductivity type in a surface of said substrate and spaced apart by a channel region; and forming a single, lightly doped extension of said drain region into said channel, said extension being of said second conductivity type and of a lower dopant concentration than said drain region.

Claim 13

Dependent Claim 41 words

The method of claim 9 and further including the step of forming a single halo region generally surrounding said source region in said substrate, said halo region of said first conductivity type and of a higher doping concentration than said substrate.

Claim 14

Dependent Claim 15 words

The method of claim 10 wherein said extension is proximate said surface of said substrate.

Claim 15

Dependent Claim 21 words

The method of claim 11 wherein said extension is of a shallower depth into said substrate surface than said drain region.

Claim 16

Dependent Claim 26 words

The method of claim 9 and further including the step of forming a gate electrode situated over said channel region and insulated from said channel region.

Claim 17

Dependent Claim 25 words

The method of claim 13 wherein said gate electrode generally spans said channel to overlap said drain extension, said halo region, and said source region.

Claim 18

Independent Claim 118 words

A method of forming a field effect transistor, comprising the steps of : providing a semiconductor substrate of first conductivity type; forming a generally conformal layer of gate electrode material over said device region; forming a mask over said layer of gate electrode material, said mask including a generally vertical edge situated over said substrate; forming a first device region in a portion of said substrate self-aligned with said mask; using said mask to define a gate electrode from said layer of gate electrode material while exposing a previously masked portion of said substrate adjoining said gate electrode; and forming a second device region type in the newly exposed portion of said substrate self-aligned with said gate electrode.

Claim 19

Independent Claim 118 words

A method of forming a field effect transistor, comprising the steps of : providing a semiconductor substrate of first conductivity type; forming a generally conformal layer of gate electrode material over said device region; forming a mask over said layer of gate electrode material, said mask including a generally vertical edge situated over said substrate; forming a first device region in a portion of said substrate self-aligned with said mask; using said mask to define a gate electrode from said layer of gate electrode material while exposing a previously masked portion of said substrate adjoining said gate electrode; and forming a second device region type in the newly exposed portion of said substrate self-aligned with said gate electrode.

Claim 20

Dependent Claim 26 words

A method in accordance with claim 15 wherein said steps of forming said first and second regions include implanting ions into said surface of said substrate.

Claim 21

Dependent Claim 46 words

A method in accordance with claim 15 wherein: said step of forming a mask includes forming a side-wall on said mask edge; and said step of using said mask to define a gate electrode includes the step of using said side-wall to define said gate electrode.

Claim 22

Dependent Claim 29 words

A method in accordance with claim 15 and further including the step of forming a layer of insulating material intermediate said substrate and said layer of gate electrode material.

Claim 23

Dependent Claim 57 words

A method in accordance with claim 15 wherein said step of forming said first region includes the steps of : implanting a halo region of said first conductivity type into said substrate; and implanting a source region of said second conductivity type into said substrate, such that said halo region surrounds said source region in said substrate.

Claim 24

Dependent Claim 72 words

A method in accordance with claim 15 wherein said step of forming said second region includes the steps of : implanting a lightly doped extension of said second conductivity type into said substrate; forming a sidewall of protective material on the edge of said gate electrode overlying said extension; and depositing a drain region of said second conductivity type into said substrate using said gate electrode and said sidewall as a mask.

Claim 25

Independent Claim 168 words

A method of forming a field effect transistor comprising the steps of : providing a semiconductor substrate of first conductivity type; forming a layer of insulating material over said substrate; forming a layer of gate electrode material over said layer of insulating material; forming a layer of first mask material over said gate electrode material such that a generally vertical edge of said first mask material over-lies said substrate; forming a sidewall of second mask material on said edge of said layer of first mask material; forming a first device region in a portion of said substrate not covered by said first or second mask materials; removing said layer of first mask material so as to leave said sidewall of second mask material; using said sidewall as a mask to define a gate structure from said layers of gate electrode and insulating material; and forming a second device region adjoining said gate structure in the portion of said substrate exposed by removing said layer of first mask material.

Claim 26

Independent Claim 168 words

A method of forming a field effect transistor comprising the steps of : providing a semiconductor substrate of first conductivity type; forming a layer of insulating material over said substrate; forming a layer of gate electrode material over said layer of insulating material; forming a layer of first mask material over said gate electrode material such that a generally vertical edge of said first mask material over-lies said substrate; forming a sidewall of second mask material on said edge of said layer of first mask material; forming a first device region in a portion of said substrate not covered by said first or second mask materials; removing said layer of first mask material so as to leave said sidewall of second mask material; using said sidewall as a mask to define a gate structure from said layers of gate electrode and insulating material; and forming a second device region adjoining said gate structure in the portion of said substrate exposed by removing said layer of first mask material.

Claim 27

Dependent Claim 54 words

A method in accordance with claim 21 wherein said step of forming said first device region includes the steps of : implanting a halo region of said first conductivity type into said substrate; and implanting a source region of second conductivity type into said substrate such that said halo region surrounds said source region.

Claim 28

Dependent Claim 81 words

A method in accordance with claim 21 wherein said step of forming said second device region includes the steps of : implanting a lightly doped region of said second conductivity type in said substrate; implanting a sidewall of protective material on the edge of said gate structure overlying said lightly doped region; and implanting a drain region of said second conductivity type in said substrate adjoining said sidewall such that said lightly doped region comprises an extension for said drain region.

Claim 29

Dependent Claim 27 words

A method in accordance with claim 21 wherein: said substrate comprises silicon semiconductor material; said insulating layer comprises SiO₂; and said gate electrode material comprises doped polysilicon.

Claim 30

Dependent Claim 23 words

A method in accordance with claim 21 wherein: said first mask material comprises a photoresist material; and said second mask material comprises Si₃N₄.

Field-effect-transistor with asymmetrical structure

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