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US 7,067,384 B1Granted
Method of forming a varactor with an increased linear tuning range
AssigneeNational Semiconductor Corporation
InventorsVladislav Vashchenko, Pascale Francis, Peter J. Hopper
Life of this patent
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Abstract
The linear tuning range of a semiconductor varactor is substantially increased by forming a lightly-doped drain region of a first conductivity type in a semiconductor material of a second conductivity type between a heavily-doped diffusion of the second conductivity type and a lower-plate region of the semiconductor material.
Claims15
A method of forming a varactor in a first semiconductor region, the first semiconductor region having a first conductivity type and a first dopant concentration, the method comprising:
- forming a layer of isolation material over the first semiconductor region;
- forming a layer of second semiconductor material on the layer of isolation material;
- etching the layer of second semiconductor material to form a first gate on the layer of isolation material;
- forming a first diffusion region in the first semiconductor region to contact the first semiconductor region, the first diffusion region having a second conductivity type and a second dopant concentration;
- forming a spacer over the first diffusion region to adjoin the first gate;
- and
- forming a second diffusion region in the first semiconductor region to contact the first semiconductor region and adjoin the first diffusion region, the second diffusion region being formed after the first diffusion region, and having the first conductivity type and a third dopant concentration that is greater than the first dopant concentration.
4 more elements
Dependencies are inferred from the claim text.