Dual-counterdoped channel field effect transistor and method
First Claim
1. A method for forming a field effect transistor, comprising the steps of:
- providing a region of semiconductor material doped a first conductivity type;
forming spaced apart source/drain pockets of said first conductivity type in said region of semiconductor material and counterdoped regions of opposite conductivity type disposed within each of said source/drain pockets forming source/drains; and
forming a channel region disposed in said region of semiconductor material between said source/drain pockets, said channel region having a first region of one of undoped or doped opposite conductivity type and a second doped region underlying the first region of said opposite conductivity type and having a greater charge-carrier mobility than said first region, said second doped region being the primary conduction channel between said source and said drain.
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Abstract
A field effect transistor with a dual-counterdoped channel is disclosed. The transistor features a channel comprising a first doped region (28) and a second doped region (26) underlying the first doped region. A source and drain (32) are formed adjacent to the channel. In one embodiment of the present invention, the first doped region (28) is doped with arsenic, while the second doped region (26) is doped with phosphorus. The high charge-carrier mobility of the subsurface channel layer (28) allowing a lower channel dopant concentration to be used, which in turn allows lower source/drain pocket doping. This reduces the capacitance and response time of the transistor.
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Citations
9 Claims
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1. A method for forming a field effect transistor, comprising the steps of:
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providing a region of semiconductor material doped a first conductivity type;
forming spaced apart source/drain pockets of said first conductivity type in said region of semiconductor material and counterdoped regions of opposite conductivity type disposed within each of said source/drain pockets forming source/drains; and
forming a channel region disposed in said region of semiconductor material between said source/drain pockets, said channel region having a first region of one of undoped or doped opposite conductivity type and a second doped region underlying the first region of said opposite conductivity type and having a greater charge-carrier mobility than said first region, said second doped region being the primary conduction channel between said source and said drain. - View Dependent Claims (2, 3, 4)
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5. A method for forming a field effect transistor, comprising the steps of:
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providing a region of semiconductor material doped a first conductivity type;
forming a source region of said first conductivity type and a drain region of said first conductivity type, both said source region and said drain region disposed in said region of semiconductor material and separated by a channel region disposed in said region of semiconductor material;
providing said channel region by forming a first region in said channel region of one of undoped or opposite conductivity counterdoped type; and
doping said channel region with a dopant to form a second counterdoped region underlying the first region of said opposite conductivity type, said second doped region having a greater charge-carrier mobility than said first region, said second doped region being the primary conduction channel between said source region and said drain region. - View Dependent Claims (6, 7, 8, 9)
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Specification