Fabrication of complementary field-effect transistors each having multi-part channel
First Claim
1. A method of fabricating a complementary transistor structure from a semiconductive body having a device region of a first conductivity type and a device region of a second conductivity type opposite to the first conductivity type, the structure including (a) first source and drain zones of the second conductivity type laterally separated by a first channel zone in the first device region, the first drain zone comprising a first main drain portion and a more lightly doped first drain extension located between the first channel zone and the first main drain portion, the first channel zone comprising a first output channel portion and a more heavily doped first input channel portion that respectively meet the first drain extension and the first source zone, and (b) second source and drain zones of the first conductivity type laterally separated by a second channel zone in the second device region, the second drain zone comprising a second main drain portion and a more lightly doped second drain extension located between the second channel zone and the second main drain portion, the second channel zone comprising a second output channel portion and a more heavily doped second input channel portion that respectively meet the second drain extension and the second source zone, the method comprising the steps of:
- providing first and second gate electrodes respectively above, and insulatingly spaced apart from, the first and second device regions;
introducing first semiconductor dopant of the first conductivity type simultaneously (a) into part of the first channel zone to define the first input channel portion and (b) into part of the second device region to define the second drain extension;
introducing second semiconductor dopant of the second conductivity type simultaneously (a) into part of the second channel zone to define the second input channel portion and (b) into part of the first device region to define the first drain extension; and
introducing (a) third semiconductor dopant of the second conductivity type into a pair of laterally separated parts of the first device region to define the first source zone and the first main drain portion continuous with the first drain extension and (b) fourth semiconductor dopant of the first conductivity type into a pair of laterally separated parts of the second device region to define the second source zone and the second main drain portion continuous with the second drain extension.
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Abstract
Each of a pair of complementary insulated-gate field-effect transistors is manufactured in an asymmetric lightly doped drain structure that enables the source characteristics to be decoupled from the drain characteristics. Each transistor has a multi-part channel formed with an output portion, which adjoins the drain zone, and a more heavily doped input portion, which adjoins the source zone. The drain zone of each transistor contains a main portion and a more lightly doped extension that meets the output channel portion. The drain extension of each transistor typically extends at least as far below the upper semiconductor surface as the main drain portion so as to help reduce hot-carrier effects. The input channel portion of each transistor is situated in a threshold body zone whose doping determines the threshold voltage. Importantly, the provision of lightly doped source extensions is avoided so that improving the drain characteristics does not harm the source characteristics, and vice versa. In fabricating the complementary transistor structure, the threshold body zone of each transistor is formed at the same time as the drain extension of the other transistor.
142 Citations
12 Claims
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1. A method of fabricating a complementary transistor structure from a semiconductive body having a device region of a first conductivity type and a device region of a second conductivity type opposite to the first conductivity type, the structure including (a) first source and drain zones of the second conductivity type laterally separated by a first channel zone in the first device region, the first drain zone comprising a first main drain portion and a more lightly doped first drain extension located between the first channel zone and the first main drain portion, the first channel zone comprising a first output channel portion and a more heavily doped first input channel portion that respectively meet the first drain extension and the first source zone, and (b) second source and drain zones of the first conductivity type laterally separated by a second channel zone in the second device region, the second drain zone comprising a second main drain portion and a more lightly doped second drain extension located between the second channel zone and the second main drain portion, the second channel zone comprising a second output channel portion and a more heavily doped second input channel portion that respectively meet the second drain extension and the second source zone, the method comprising the steps of:
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providing first and second gate electrodes respectively above, and insulatingly spaced apart from, the first and second device regions; introducing first semiconductor dopant of the first conductivity type simultaneously (a) into part of the first channel zone to define the first input channel portion and (b) into part of the second device region to define the second drain extension; introducing second semiconductor dopant of the second conductivity type simultaneously (a) into part of the second channel zone to define the second input channel portion and (b) into part of the first device region to define the first drain extension; and introducing (a) third semiconductor dopant of the second conductivity type into a pair of laterally separated parts of the first device region to define the first source zone and the first main drain portion continuous with the first drain extension and (b) fourth semiconductor dopant of the first conductivity type into a pair of laterally separated parts of the second device region to define the second source zone and the second main drain portion continuous with the second drain extension. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification