Integrated circuit varactor having a wide capacitance range
First Claim
1. A semiconductor integrated circuit (IC) device comprising:
- a) a substrate;
b) a first insulating layer formed on the substrate;
c) a first semiconductor layer formed on the insulating layer;
d) one of an N-well and P-well implant layer formed in the first semiconductor layer;
e) a first region of one of an N+ and a P+ implant formed in the one of an N-well and P-well implant layer;
f) a second region of one of an N+ and a P+ implant formed in the one of an N-well and P-well implant layer;
g) a second insulating layer formed over a selected portion of a surface of the one of an N-well and P-well implant layer;
h) a second semiconductor layer formed over a selected portion of a surface of the second insulating layer, and between the first region and the second region, wherein the second semiconductor layer forms one of a P-gate and an N-gate; and
i) an isolation region extending from the first insulating layer to the second insulating layer and surrounding and electrically isolating the implant layer, the implant regions, and the second semiconductor layer.
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Accused Products
Abstract
Integrated circuit varactor structures that include either an P-gate/N-well or N-gate/P-well layer configuration formed on an SOI substrate. The varactor structure is completely electrically isolated from the substrate of the IC by an oxide layer of the SOI substrate and by oxide-filled trenches formed on both sides of the varactor structures. The isolation trenches preferably extend to the oxide layer of the SOI substrate. The P-gate/N-well varactor structure includes N+ implant regions formed in an N-well implant layer of the varactor. The N+ implant regions comprise the source and the drain of a varactor. A LOCOS layer may be formed over the N-well layer where the P-gate is formed over the LOCOS layer. The P-gate may be formed of polysilicon. The N-gate/P-well varactor structure includes P+ implant regions formed in a P-well implant layer of the varactor. The P+ implant regions comprise the source and the drain of a varactor. A LOCOS layer may be formed over the P-well layer where the N-gate is formed over the LOCOS layer. The N-gate may be formed of polysilicon. The P-gate/N-well varactor is ideally suited for use as a binary or digitally-controlled varactor because it abruptly changes from a first lower capacitance of C1 to a second higher capacitance of C2 as the D.C. control voltage is varied from a first to a second threshold level. In contrast, the N-gate/P-well varactor finds utility as an analog timing varactor of a fully integrated VCO device, for example, because it slowly changes from a first lower capacitance of C1 to a second higher capacitance of C2 as the D.C. control voltage is varied from low to high threshold voltage levels.
129 Citations
27 Claims
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1. A semiconductor integrated circuit (IC) device comprising:
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a) a substrate;
b) a first insulating layer formed on the substrate;
c) a first semiconductor layer formed on the insulating layer;
d) one of an N-well and P-well implant layer formed in the first semiconductor layer;
e) a first region of one of an N+ and a P+ implant formed in the one of an N-well and P-well implant layer;
f) a second region of one of an N+ and a P+ implant formed in the one of an N-well and P-well implant layer;
g) a second insulating layer formed over a selected portion of a surface of the one of an N-well and P-well implant layer;
h) a second semiconductor layer formed over a selected portion of a surface of the second insulating layer, and between the first region and the second region, wherein the second semiconductor layer forms one of a P-gate and an N-gate; and
i) an isolation region extending from the first insulating layer to the second insulating layer and surrounding and electrically isolating the implant layer, the implant regions, and the second semiconductor layer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A semiconductor integrated circuit (IC) device comprising:
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a) a substrate;
b) a first insulating layer formed on the substrate;
c) a first semiconductor layer formed on the insulating layer;
d) an N-well implant layer formed in the first semiconductor layer;
e) a first region of an N+ implant formed in the N-well implant layer;
f) a second region of an N+ implant formed in the N-well implant layer;
g) a second insulating layer form over a selected portion of a surface of the N-well implant layer;
h) a second semiconductor layer formed over a selected portion of the surface of the second insulating layer, and between the first region and the second region, wherein the second semiconductor layer forms a P-gate; and
i) an isolation region extending from the first insulating layer to the second insulating layer and surrounding and electrically isolating the implant layer, the implant regions, and the second semiconductor layer. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A semiconductor integrated circuit (IC) device comprising:
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a) a substrate;
b) a first insulating layer formed on the substrate;
c) a first semiconductor layer formed on the insulating layer;
d) a P-well implant layer formed in the first semiconductor layer;
e) a first region of an P+ implant formed in the P-well implant layer;
f) a second region of an P+ implant formed in the P-well implant layer;
g) a second insulating layer formed over a selected portion of a surface of the P-well implant layer;
h) a second semiconductor layer formed over a selected portion of a surface of the second insulating layer and between the first region and the second region, wherein the second semiconductor layer forms an N-gate;
i) an isolation region extending from the first insulating layer to the second insulating layer and surrounding and electrically isolating the implant layer, the implant regions, and the second semiconductor layer. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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Specification