A semiconductor element includes a high-resistivity substrate that includes a β-Ga.sub.2O.sub.3-based single crystal including an acceptor impurity, an undoped β-Ga.sub.2O.sub.3-based single crystal layer formed on the high-resistivity substrate, and an n-type channel layer that includes a side surface surrounded by the undoped β-Ga.sub.2O.sub.3-based single crystal layer. The undoped β-Ga.sub.2O.sub.3-based single crystal layer includes an element isolation region.

A semiconductor element includes a high-resistivity substrate that includes a β-Ga.sub.2O.sub.3-based single crystal including an acceptor impurity, a buffer layer on the high-resistivity substrate, the buffer layer including a β-Ga.sub.2O.sub.3-based single crystal, and a channel layer on the buffer layer, the channel layer including a β-Ga.sub.2O.sub.3-based single crystal including a donor impurity. A crystalline laminate structure includes a high-resistivity substrate that includes a β-Ga.sub.2O.sub.3-based single crystal including an acceptor impurity, a buffer layer on the high-resistivity substrate, the buffer layer including a β-Ga.sub.2O.sub.3-based single crystal, and a donor impurity-containing layer on the buffer layer, the donor impurity-containing layer including a β-Ga.sub.2O.sub.3-based single crystal including a donor impurity.

A multilayer structure with excellent crystallinity and a semiconductor device of the multilayer structure with good mobility are provided. A multilayer structure includes: a corundum structured crystal substrate; and a crystalline film containing a corundum structured crystalline oxide as a major component, the film formed directly on the substrate or with another layer therebetween, wherein the crystal substrate has an off angle from 0.2° to 12.0°, and the crystalline oxide contains one or more metals selected from indium, aluminum, and gallium.

A vertical semiconductor transistor and a method of forming the same. A vertical semiconductor transistor has at least one semiconductor region, a source, and at least one gate region. The at least one semiconductor region includes a III-nitride semiconductor material. The source is formed over the at least one semiconductor region. The at least one gate region is formed around at least a portion of the at least one semiconductor region.

With a microwave FET, an incorporated Schottky junction capacitance or PN junction capacitance is small and such a junction is weak against static electricity. However, with a microwave device, the method of connecting a protecting diode cannot be used since this method increases the parasitic capacitance and causes degradation of the high-frequency characteristics. In order to solve the above problems, a protecting element, having a first n.sup.+-type region—insulating region—second n.sup.+-type region arrangement is connected in parallel between two terminals of a protected element having a PN junction, Schottky junction, or capacitor. Since discharge can be performed between the first and second n.sup.+ regions that are adjacent each other, electrostatic energy that would reach the operating region of an FET can be attenuated without increasing the parasitic capacitance.

With a microwave FET, an incorporated Schottky junction capacitance or PN junction capacitance is small and such a junction is weak against static electricity. However, with a microwave device, the method of connecting a protecting diode cannot be used since this method increases the parasitic capacitance and causes degradation of the high-frequency characteristics. In order to solve the above problems, a protecting element, having a first n.sup.+-type region—insulating region—second n.sup.+-type region arrangement is connected in parallel between two terminals of a protected element having a PN junction, Schottky junction, or capacitor. Since discharge can be performed between the first and second n.sup.+ regions that are adjacent each other, electrostatic energy that would reach the operating region of an FET can be attenuated without increasing the parasitic capacitance.

A high-frequency conductor having improved conductivity comprises at least one electrically conductive base material. The ratio of the outer and inner surfaces of the base material permeable by a current to the total volume of the base material is increased by a) dividing the base material perpendicularly to the direction of current into at least two segments, which are spaced from each other by an electrically conductive intermediate piece and connected both electrically and mechanically to each other, and/or b) topographical structures in or on the surface of the base material and/or c) inner porosity of at least a portion of the base material compared to a design of the base material in which the respective feature was omitted. It was found that, as a result of these measures concerning the design, it is possible to physically arrange the same amount abase material so that a larger fraction of the base material is located at a distance of no more than skin depth from an outer or inner surface and is thus involved in current transport. As a result, a lesser fraction remains unused as a function of the skin effect.

A high-frequency conductor having improved conductivity comprises at least one electrically conductive base material. The ratio of the outer and inner surfaces of the base material permeable by a current to the total volume of the base material is increased by a) dividing the base material perpendicularly to the direction of current into at least two segments, which are spaced from each other by an electrically conductive intermediate piece and connected both electrically and mechanically to each other, and/or b) topographical structures in or on the surface of the base material and/or c) inner porosity of at least a portion of the base material compared to a design of the base material in which the respective feature was omitted. It was found that, as a result of these measures concerning the design, it is possible to physically arrange the same amount abase material so that a larger fraction of the base material is located at a distance of no more than skin depth from an outer or inner surface and is thus involved in current transport. As a result, a lesser fraction remains unused as a function of the skin effect.

To provide an inspection device and an inspection method which are capable of detecting a disconnection defect in an organic TFT array and/or evaluating a variation in the output properties and response speed of each organic TFT element. There are provided a device and a method of optically measuring the presence or absence of the accumulation of carriers in an organic semiconductor thin film which provides a channel layer of an organic TFT element. A source and a drain in each organic TFT are short-circuited to each other, a voltage is turned on and turned off in a predetermined period between this and a gate, and images before and after application of the voltage are captured in synchronization with the predetermined period while radiating monochromatic light, to obtain a differential image.

A silicon carbide substrate has a first main surface, and a second main surface opposite to the first main surface. A region including at least one main surface of the first and second main surfaces is made of single-crystal silicon carbide. In the one main surface, sulfur atoms are present at not less than 60×10.sup.10 atoms/cm.sup.2 and not more than 2000×10.sup.10 atoms/cm.sup.2, and carbon atoms as an impurity are present at not less than 3 at % and not more than 25 at %. Thereby, a silicon carbide substrate having a stable surface, a semiconductor device using the substrate, and methods for manufacturing them can be provided.