Placement of a field plate in a field-effect transistor is optimized by using multiple dielectric layers such that a first end of field plate is separated from a channel region of the transistor by a first set of one or more distinct dielectric material layers. A second end of the field plate overlies the channel region and a control electrode from which it is separated by the first set of dielectric layers and one or more additional dielectric layers.

A method includes: forming a trench in a first major surface of a semiconductor substrate, the trench having a base and a side wall extending from the base to the first major surface; forming a first insulating layer on the trench base and side wall; forming a sacrificial layer on the first insulating layer on the trench side wall; forming a second insulation layer on the sacrificial layer; inserting conductive material into the trench that at least partially covers the second insulation layer; selectively removing portions of the second insulation layer uncovered by the conductive material; selectively removing the sacrificial layer to form a recess that is positioned adjacent the conductive material in the trench and that is bounded by the first insulation layer and the second insulating layer; and forming a third insulating layer in the trench that caps the recess to form an enclosed cavity in the trench.

A method includes: forming a trench in a first major surface of a semiconductor substrate, the trench having a base and a side wall extending from the base to the first major surface; forming a first insulating layer on the trench base and side wall; forming a sacrificial layer on the first insulating layer on the trench side wall; forming a second insulation layer on the sacrificial layer; inserting conductive material into the trench that at least partially covers the second insulation layer; selectively removing portions of the second insulation layer uncovered by the conductive material; selectively removing the sacrificial layer to form a recess that is positioned adjacent the conductive material in the trench and that is bounded by the first insulation layer and the second insulating layer; and forming a third insulating layer in the trench that caps the recess to form an enclosed cavity in the trench.

A device includes a buried oxide layer disposed on a substrate, a first region disposed on the buried oxide layer and a first ring region disposed in the first region. The first ring region includes a portion of a guardring. The device further includes a first terminal region disposed in the first ring region, a second ring region disposed in the first region and a second terminal region disposed in the second ring region. The first terminal region is connected to an anode and the second terminal region is connected to a cathode. The first region has a graded doping concentration. The first region, the second ring region and the second terminal region have a first conductivity type, and the first ring region and the first terminal region have a second conductivity type. The first conductivity type is different from the second conductivity type.

A device includes a buried oxide layer disposed on a substrate, a first region disposed on the buried oxide layer and a first ring region disposed in the first region. The first ring region includes a portion of a guardring. The device further includes a first terminal region disposed in the first ring region, a second ring region disposed in the first region and a second terminal region disposed in the second ring region. The first terminal region is connected to an anode and the second terminal region is connected to a cathode. The first region has a graded doping concentration. The first region, the second ring region and the second terminal region have a first conductivity type, and the first ring region and the first terminal region have a second conductivity type. The first conductivity type is different from the second conductivity type.

A III-N device is described with a III-N material layer, an insulator layer on a surface of the III-N material layer, an etch stop layer on an opposite side of the insulator layer from the III-N material layer, and an electrode defining layer on an opposite side of the etch stop layer from the insulator layer. A recess is formed in the electrode defining layer. An electrode is formed in the recess. The insulator can have a precisely controlled thickness, particularly between the electrode and III-N material layer.

A III-N device is described with a III-N material layer, an insulator layer on a surface of the III-N material layer, an etch stop layer on an opposite side of the insulator layer from the III-N material layer, and an electrode defining layer on an opposite side of the etch stop layer from the insulator layer. A recess is formed in the electrode defining layer. An electrode is formed in the recess. The insulator can have a precisely controlled thickness, particularly between the electrode and III-N material layer.

An integrated circuit (IC) having a fin field effect transistor (FinFET) includes a substrate with a fin extending from a surface of the substrate. The fin includes a source region, a drain region, a drift region, and field plating oxide layer. The drift region is adjacent the drain region. The field plating oxide layer is on a first side, a second side, and a third side of the drift region.

An integrated circuit (IC) having a fin field effect transistor (FinFET) includes a substrate with a fin extending from a surface of the substrate. The fin includes a source region, a drain region, a drift region, and field plating oxide layer. The drift region is adjacent the drain region. The field plating oxide layer is on a first side, a second side, and a third side of the drift region.

A Group III nitride-based transistor device is provided that has a gate drain capacitance (C.sub.GD), a drain source capacitance (C.sub.DS) and a drain source on resistance (RDSon). A ratio of the gate drain capacitance (C.sub.GD) at a drain source voltage (V.sub.DS) of 0V, C.sub.GD (0V), and the gate drain capacitance C.sub.GD at a value of V.sub.DS>0V, C.sub.GDV, is at least 3:1, wherein VDS is less than 15V.