A variable capacitor includes a mesa on a substrate. The mesa has multiple III-V semiconductor layers and includes a first side and a second side opposite the first side. The first side has a first sloped portion and a first horizontal portion. The second side has a second sloped portion and a second horizontal portion. A control terminal is on a third side of the mesa. A first terminal is on the first side of the mesa. The first terminal is disposed on the first horizontal portion and the first sloped portion. A second terminal is also on the substrate.

A structure for improved noise signal isolation in semiconductor devices. In one embodiment, the structure includes a second-conductivity type substrate, a 1.sup.st first-conductivity type well, a 1.sup.st first-conductivity type layer, a second-conductivity type layer positioned between the 1.sup.st first-conductivity type well and the 1.sup.st first-conductivity type layer. The structure also includes a 2.sup.nd first-conductivity type well, and a 2.sup.nd first-conductivity type layer positioned between the 2.sup.nd first-conductivity type well and the 1.sup.st first-conductivity type layer. The 1.sup.st first-conductivity type layer and the second-conductivity type layer are positioned between the P type substrate and the 1.sup.st first-conductivity type well, and the 1.sup.st first-conductivity type well is laterally separated from the 2.sup.nd first-conductivity type well.

An integrated circuit includes an SOI substrate having a semiconductor layer over a buried insulator layer; the semiconductor layer contains white space regions that include a PWELL region. An electronic device includes an NWELL region in the semiconductor layer, a dielectric over the NWELL region, and a polysilicon plate over the dielectric. A sacrificial NWELL ring is adjacent to and separated from the NWELL region by a first gap.

Certain aspects of the present disclosure provide a semiconductor variable capacitor. The semiconductor variable capacitor generally includes a first semiconductor region having a first doping type, a second semiconductor region having a second doping type different from the first doping type, a third semiconductor region disposed between the first semiconductor region and the second semiconductor region, a first terminal disposed adjacent to the first semiconductor region, a second terminal disposed adjacent to the second semiconductor region, and a third terminal disposed above the third semiconductor region. The first semiconductor region, the second semiconductor region, and/or the third semiconductor region include gallium nitride. The third semiconductor region includes multiple semiconductor layers having different materials. A capacitance between the first terminal and the third terminal is configured to be adjusted by varying a control voltage applied to at least one of the first terminal or the second terminal.

An integrated circuit includes a substrate having a first conductivity type. A well formed at an upper surface has a second, opposite conductivity type and a first dopant concentration. First and second STI structures are formed and a polysilicon gate structure is formed between the first and second STI structures. The polysilicon gate structure extends over a first side of the first STI structure and over a first side of the second STI structure. A first doped region is formed within the well at the upper surface and on a second side of the first STI structure and a second doped region is formed within the well at the upper surface and on a second side of the second STI structure. The first and second doped regions each have the second conductivity type and a second dopant concentration that is greater than the first dopant concentration.

In certain aspects, a variable capacitor comprises a well having a first side and a second side, an N+ diffusion abutted the well at the first side, a P+ diffusion abutted the well at the second side, and an insulator on the well. The variable capacitor further comprises a gate plate on the insulator having a first gate segment and a second gate segment, wherein the first gate segment and the second gate segment are configured to have different work functions.

An integrated circuit includes an SOI substrate having a semiconductor layer over a buried insulator layer; the semiconductor layer contains white space regions that include a PWELL region. An electronic device includes an NWELL region in the semiconductor layer, a dielectric over the NWELL region, and a polysilicon plate over the dielectric. A sacrificial NWELL ring is adjacent to and separated from the NWELL region by a first gap.

Certain aspects of the present disclosure provide a semiconductor device. One example semiconductor device generally includes a first semiconductor region; a first non-insulative region disposed adjacent to a first lateral side of the first semiconductor region; a second non-insulative region disposed adjacent to a second lateral side of the first semiconductor region, the second lateral side being opposite to the first lateral side; a second semiconductor region disposed adjacent to a third lateral side of the first semiconductor region, the second semiconductor region and the first semiconductor region having at least one of different doping types or different doping concentrations; an insulative layer adjacent to a top side of the first semiconductor region; and a third non-insulative region, the insulative layer being disposed between the third non-insulative region and the first semiconductor region.

Various embodiments of the present disclosure are directed towards a method for forming a varactor comprising a reduced surface field (RESURF) region. The method includes forming a drift region having a first doping type within a substrate. A RESURF region having a second doping type is formed within the substrate such that the RESURF region is below the drift region. A gate structure is formed on the substrate. A pair of contact regions is formed within the substrate on opposing sides of the gate structure. The contact regions respectively abut the drift region and have the first doping type, and wherein the first doping type is opposite the second doping type.

Certain aspects of the present disclosure provide semiconductor variable capacitors. One example semiconductor variable capacitor generally includes a semiconductor region, an insulative layer, and a first non-insulative region, the insulative layer being disposed between the semiconductor region and the first non-insulative region. In certain aspects, the semiconductor variable capacitor may also include a second non-insulative region disposed adjacent to the semiconductor region, and a third non-insulative region disposed adjacent to the semiconductor region, the second non-insulative region and the third non-insulative region having different doping types. In certain aspects, the semiconductor variable capacitor may also include an implant region disposed between the semiconductor region and the insulative layer. The implant region may be used to adjust the flat-band voltage of the semiconductor variable capacitor.