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US 2003/0197216 A1Published application
pn Varactor
AssigneeFujitsu Limited
InventorKoji Kudo
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AssigneeFujitsu Limited
InventorKoji Kudo
Estimating the term…
An object of this invention is to provide a pn-varactor having a small resistance and capable of coinciding with incorporation of a circuit employing LC resonance into an integrated circuit. A dummy gate pattern 4 is formed over a n-well 1 in a semiconductor wafer and then p+ diffusion regions 2, 3 are formed on both sides with the dummy gate pattern 4 as inhibition mask. For the purpose, a control voltage VT higher than potentials of the p+ diffusion regions 2, 3 is applied to the n-well 1. Consequently, both the pn-junction between the n-well 1 and the p+ diffusion region 2 and the pn-junction between the n-well 1 and the p+ diffusion region 3 act as a pn-varactor whose capacity is changed by the control voltage VT. If an end dummy pattern is provided on both sides or around the p+ diffusion regions 2, 3, imbalance in capacity due to deflection in position is prevented.
A pn varactor using pn junctions as variable capacitance capacitor, the pn varactor comprising:
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
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Capacitors having potential barriers: variable-capacitance diodes, e.g. varactors
The amplifier comprising a pair of transistors, wherein an output terminal of each being connected to an input terminal of the other, e.g. a…
Active element in amplifier being semiconductor device: the amplifier comprising one or more bipolar transistors
The means comprising a voltage dependent capacitance: the means comprising voltage variable capacitance diodes
Term end not estimated
This application is based upon and claims the benefit of priority from each of the prior Japanese Patent Application No. 2002-116699 filed on Apr. 18, 2002, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a pn varactor that uses a pn junction as variable capacitance capacitor. More particularly, it relates to a pn varactor that has a small resistance and can cope with being built in an integrated circuit of a circuit that uses LC resonance.
FIG. 1 is a plan view and a sectional view showing most typical structure of a differential pn varactor directed to an embodiment;
FIG. 2 is an equivalent circuit diagram of the differential pn varactor directed to the embodiment;
FIG. 3 is a plan view and a sectional view showing structure of a differential pn varacor with end dummy pattern arranged on both sides;
Hereinafter, the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. According to this embodiment, the present invention is embodied in a varactor section in case where the VCO circuit as shown in FIG. 10 is built in an integrated circuit.
[First Embodiment]
FIG. 1 shows a plan view and a sectional view of a differential pn-varactor according to the first embodiment. This differential pn-varactor includes two p+ diffusion regions 2, 3 in a n-well 1. A dummy gate pattern 4 is provided over a region between the p+ diffusion regions 2 and 3. Further, the dummy gate pattern 4 and the n-well 1 are connected through a wiring 10.