Voltage controlled variable area solid state tuning capacitor

Claim 2

A solid state two electrode parallel plate-type variable area varactor that provides a large change in capacitance by increasing the effective area of a region in a semiconductive body portion in which said region serves as one plate of the parallel plate varactor, said varactor comprising a semiconductor body having a major surface, a region of one conductivity type semiconductive material disposed within said body and intersecting said major surface, said region having an effective area which serves as a variable area plate for said parallel plate varactor, portions of said body including said major surface contiguous said region being of an opposite conductivity type, a layer of dielectric material on parts of said region and contiguous major surface portions, only two electrodes on said varactor for receiving a variable voltage thereto and for supplying the output capacitance thereof, a first electrode on said dielectric overlying parts of said region and an area of said body portions contiguous said region, said first electrode serving as a fixed area opposite plate for said parallel plate varactor in which the area of said first electrode overlying said region determines the minimum capacitance for said varactor irrespective of doping levels in said contiguous body portions, a second electrode on said region electrically insulated from said first electrode, said body portions being electrode-free whereby said body portions will electrically float with voltages applied between said first and second electrodes, said varactor having an entire range of output capacitance that varies directly with the area of said first electrode overlying the effective area of said region, said effective area underlying said first electrode expandable as a direct function of an applied controlling voltage between said first and second electrodes having a polarity at said second electrode which is the same as the conductivity type of said region and having a polarity at said first electrode so as to invert the conductivity type of the semiconductive material of said contiguous body portions underlying said first electrode to the same conductivity type as said region, thereby progressively increasing the effective area of said region and the capacitance of said varactor.

Claim 3

A solid state two electrode parallel plate-type variable area varactor suitable for AM radio frequency band tuning that provides a maximum to minimum capacitance ratio greater than 4:1 by increasing the effective area of an island region in a semiconductor body in which said island region serves as one plate of the parallel plate varactor, said varactor comprising a body of semiconductive material having a generally flat major surface, portions of said body including said major surface being of one conductivity type, an island region of an opposite conductivity type semiconductive material, said island region having a generally flat face, said island region being disposed within a centrally located portion of said major surface of said body wherein said face of said island region is coplanar with said major surface of said body, said region having an effective area which serves as a variable area plate for said parallel plate varactor, a layer of dielectric material on said major surface of said body circumscribing said face of said island region, said dielectric layer overlying peripheral portions of said island region, only two electrodes on said varactor for receiving a variable voltage thereto and for supplying the output capacitance thereof, a first electrode on said dielectric circumscribing said face of said island region, said first electrode overlying said peripheral portions of said island region and an area of said body portions contiguous said island region, said first electrode serving as a fixed area opposite plate for said parallel plate varactor in which the area of said first electrode overlying said island region determines the minimum capacitance for said varactor irrespective of doping levels in said contiguous body portions, a second electrode on said island region electrically insulated from said field plate, said body portions being electrode-free whereby said body portions will electrically float with voltages applied to said first and second electrodes, said varactor having an entire range of output capacitance that varies directly with the area of said first electrode which overlies said effective area of the island region, said effective area underlying said field plate being expandable by applying a voltage between said first and second electrodes having a polarity at said second electrode which is the same as the conductive type of said island region and at said first electrode so as to progressively invert the semiconductive material of the area of said contiguous body portions underlying the first electrode to the same conductivity type of said island region, and thereby progressively increase the entire range of output capacitance of said varactor as a direct function of the applied voltage.

Claim 4

A solid state two electrode parallel plate-type variable area varactor suitable for AM radio frequency band tuning that provides a maximum to minimum capacitance ratio greater than 4:1 by increasing the effective area of an island region in a semiconductor body in which said island region serves as one plate of the parallel plate varactor, said varactor comprising a body of semiconductive material having a generally flat major surface, portions of said body including said major surface being of one conductivity type, an island region of an opposite conductivity type semiconductive material, said island region having a generally flat face, said island region being disposed within a centrally located portion of said major surface of said body wherein said face of said island region is coplanar with said major surface of said body, said region having an effective area which serves as a variable area plate for said parallel plate varactor, a layer of dielectric material on said major surface of said body circumscribing said face of said island region, said dielectric layer overlying peripheral portions of said island region, only two electrodes on said varactor for receiving a variable voltage thereto and for supplying the output capacitance thereof, a first electrode on said dielectric circumscribing said face of said island region, said first electrode overlying said peripheral portions of said island region and an area of said body portions contiguous said island region, said first electrode serving as a fixed area opposite plate for said parallel plate varactor in which the area of said first electrode overlying said island region determines the minimum capacitance for said varactor irrespective of doping levels in said contiguous body portions, a second electrode on said island region electrically insulated from said field plate, said body portions being electrode-free whereby said body portions will electrically float with voltages applied to said first and second electrodes, said varactor having an entire range of output capacitance that varies directly with the area of said first electrode which overlies said effective area of the island region, said effective area underlying said field plate being expandable by applying a voltage between said first and second electrodes having a polarity at said second electrode which is the same as the conductive type of said island region and at said first electrode so as to progressively invert the semiconductive material of the area of said contiguous body portions underlying the first electrode to the same conductivity type of said island region, and thereby progressively increase the entire range of output capacitance of said varactor as a direct function of the applied voltage.

Claim 5

An electrical circuit that provides a large change in capacitance including a distinctive solid state two electrode parallel plate-type variable area varactor having a region of semiconductive material whose effective area is a function of an applied voltage and serves as one plate of the parallel plate varactor, and a variable voltage source for applying a controlling voltage between said region and an overlying field plate electrode, said circuit comprising means for applying a variable voltage, a body of one conductivity type semiconductive material having a major surface, a region of an opposite conductivity type semiconductive material disposed within said body and intersecting said major surface, said region having an effective area serving as a variable area plate for said parallel plate varactor, a layer of dielectric material on said major surface of said body and on portions of said region, only two electrodes on said varactor for receiving said variable voltage means and for supplying the output capacitance of said varactor, a first electrode on said dielectric layer with portions thereof overlying portions of said region and an area of said body contiguous said region, said first electrode serving as a fixed area opposite plate for said parallel plate varactor in which the area of said first electrode overlying said region determines the minimum capacitance for said varactor irrespective of doping levels in said body, a second electrode on said region electrically insulated from said electrode, said means for applying the variable voltage in electrical connection only between said first and second electrodes, except for said region said body being electrode-free with no direct electrical connection to said voltage means thereby electrically floating said body, said voltage means having a polarity at said second electrode which is the same as the conductivity type of said region and of the opposite polarity at said first electrode so as to progressively invert the semiconductive material of said body underlying said first electrode contiguous said region to the same conductivity type as said region thereby progressively increasing the effective area of said region underlying said first electrode and proportionally increasing the output capacitance of said varactor, wherein the entire range of said output capacitance varies directly with the overlying area between said variable effective area of said region and said first electrode.

Claim 6

An electrical circuit that provides a large change in capacitance including a distinctive solid state two electrode parallel plate-type variable area varactor having a region of semiconductive material whose effective area is a function of an applied voltage and serves as one plate of the parallel plate varactor, and a variable voltage source for applying a controlling voltage between said region and an overlying field plate electrode, said circuit comprising means for applying a variable voltage, a body of one conductivity type semiconductive material having a major surface, a region of an opposite conductivity type semiconductive material disposed within said body and intersecting said major surface, said region having an effective area serving as a variable area plate for said parallel plate varactor, a layer of dielectric material on said major surface of said body and on portions of said region, only two electrodes on said varactor for receiving said variable voltage means and for supplying the output capacitance of said varactor, a first electrode on said dielectric layer with portions thereof overlying portions of said region and an area of said body contiguous said region, said first electrode serving as a fixed area opposite plate for said parallel plate varactor in which the area of said first electrode overlying said region determines the minimum capacitance for said varactor irrespective of doping levels in said body, a second electrode on said region electrically insulated from said electrode, said means for applying the variable voltage in electrical connection only between said first and second electrodes, except for said region said body being electrode-free with no direct electrical connection to said voltage means thereby electrically floating said body, said voltage means having a polarity at said second electrode which is the same as the conductivity type of said region and of the opposite polarity at said first electrode so as to progressively invert the semiconductive material of said body underlying said first electrode contiguous said region to the same conductivity type as said region thereby progressively increasing the effective area of said region underlying said first electrode and proportionally increasing the output capacitance of said varactor, wherein the entire range of said output capacitance varies directly with the overlying area between said variable effective area of said region and said first electrode.

Claim 7

An electrical circuit that provides a capacitance ratio of greater than 4:1 for AM radio frequency band tuning applications including a distinctive solid state two electrode parallel plate-type variable area varactor having a region of semiconductive material whose effective area is a function of an applied voltage and which serves as one plate of the parallel plate varactor, and a variable voltage source for applying a controlling voltage to said region and an overlying field plate electrode, said circuit comprising means for applying a variable voltage, a body of one conductivity type semiconductive material, said body having a generally flat major surface, an island region of an opposite conductivity type semiconductive material, said island region having a generally flat face, said island region being disposed within a centrally located portion of said major surface of said body so that said face of said island region is in the same plate thereof, said island region having an effective area serving as a variable area plate for said parallel plate varactor, a layer of dielectric material on said major surface of said body and surrounding said face of said island region with said dielectric partially overlying portions thereof, only two electrodes on said varactor for receiving said variable voltage means and for supplying the output capacitance of the varactor, a first electrode on said dielectric layer and circumscribing said face of said island region, said field plate partially overlying said face of said island region and portions of said body contiguous said island region, said first electrode serving as a fixed area opposite plate for said parallel plate varactor in which the area of said first electrode overlying said island region determines the minimum capacitance for said varactor irrespective of doping levels in said body, a second electrode on said face of said island region electrically insulated from said first electrode, said means for applying a variable voltage in electrical connection only between said first and second electrodes, except for said island region said body being electrode-free with no direct electrical connection to said voltage means thereby electrically floating said body, said voltage means having a polarity at said second electrode which is the same as the conductivity type of said island region and of an opposite polarity at said first electrode so as to progressively invert the underlying semiconductive material of said body contiguous said island region to the same conductivity type as said island region thereby progressively increasing the effective area of said island region and the output capacitance of said varactor as a direct function of said voltage means, wherein the entire range of said output capacitance varies directly with the overlying area between said variable effective area of the region and said first electrode.

Claim 8

An electrical circuit that provides a capacitance ratio of greater than 4:1 for AM radio frequency band tuning applications including a distinctive solid state two electrode parallel plate-type variable area varactor having a region of semiconductive material whose effective area is a function of an applied voltage and which serves as one plate of the parallel plate varactor, and a variable voltage source for applying a controlling voltage to said region and an overlying field plate electrode, said circuit comprising means for applying a variable voltage, a body of one conductivity type semiconductive material, said body having a generally flat major surface, an island region of an opposite conductivity type semiconductive material, said island region having a generally flat face, said island region being disposed within a centrally located portion of said major surface of said body so that said face of said island region is in the same plate thereof, said island region having an effective area serving as a variable area plate for said parallel plate varactor, a layer of dielectric material on said major surface of said body and surrounding said face of said island region with said dielectric partially overlying portions thereof, only two electrodes on said varactor for receiving said variable voltage means and for supplying the output capacitance of the varactor, a first electrode on said dielectric layer and circumscribing said face of said island region, said field plate partially overlying said face of said island region and portions of said body contiguous said island region, said first electrode serving as a fixed area opposite plate for said parallel plate varactor in which the area of said first electrode overlying said island region determines the minimum capacitance for said varactor irrespective of doping levels in said body, a second electrode on said face of said island region electrically insulated from said first electrode, said means for applying a variable voltage in electrical connection only between said first and second electrodes, except for said island region said body being electrode-free with no direct electrical connection to said voltage means thereby electrically floating said body, said voltage means having a polarity at said second electrode which is the same as the conductivity type of said island region and of an opposite polarity at said first electrode so as to progressively invert the underlying semiconductive material of said body contiguous said island region to the same conductivity type as said island region thereby progressively increasing the effective area of said island region and the output capacitance of said varactor as a direct function of said voltage means, wherein the entire range of said output capacitance varies directly with the overlying area between said variable effective area of the region and said first electrode.