A method of manufacturing a vertical metal-semiconductor field-effect transistor (MESFET) device is provided. The method includes forming a first oxide layer, forming a first electrode in the oxide layer, forming a crystallized silicon layer on the first electrode, forming a second electrode on the first oxide layer and on sidewalls of the crystalized silicon layer, forming a second oxide layer on upper surfaces of the second electrode. The method also includes forming a third electrode on an upper surface of the crystallized silicon layer.

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 high-frequency transistor includes a source electrode, a drain electrode, a gate electrode, and a gate drive line that applies a voltage to the gate electrode. An impedance adjustment circuit is connected between the gate electrode and the gate drive line. A characteristic impedance of the gate electrode is Z1, when a connecting point between the impedance adjustment circuit and the gate electrode is viewed from the impedance adjustment circuit. A characteristic impedance of the gate drive line is Z2, when a connecting point between the impedance adjustment circuit and the gate drive line is viewed from the impedance adjustment circuit. X that denotes a characteristic impedance of the impedance adjustment circuit is a value between Z1 and Z2.

A method of manufacturing a vertical metal-semiconductor field-effect transistor (MESFET) device is provided. The method includes forming a first oxide layer, forming a first electrode in the oxide layer, forming a crystallized silicon layer on the first electrode, forming a second electrode on the first oxide layer and on sidewalls of the crystalized silicon layer, forming a second oxide layer on upper surfaces of the second electrode. The method also includes forming a third electrode on an upper surface of the crystallized silicon layer.

A MESFET transistor on a horizontal substrate surface with at least one wiring layer on the substrate surface. The transistor comprises source, drain and gate electrodes which are at least partly covered by a semiconducting channel layer. The source, drain and gate electrodes optionally comprise interface contact materials for changing the junction type between each electrode and the channel. The interface between the source electrode and the channel is an ohmic junction, the interface between the drain electrode and the channel is an ohmic junction, and the interface between the gate electrode and the channel is a Schottky junction. The substrate is a CMOS substrate.

A high-frequency transistor includes a source electrode, a drain electrode, a gate electrode, and a gate drive line that applies a voltage to the gate electrode. An impedance adjustment circuit is connected between the gate electrode and the gate drive line. A characteristic impedance of the gate electrode is Z1, when a connecting point between the impedance adjustment circuit and the gate electrode is viewed from the impedance adjustment circuit. A characteristic impedance of the gate drive line is Z2, when a connecting point between the impedance adjustment circuit and the gate drive line is viewed from the impedance adjustment circuit. X that denotes a characteristic impedance of the impedance adjustment circuit is a value between Z1 and Z2.

A high-frequency transistor includes a source electrode, a drain electrode, a gate electrode, and a gate drive line that applies a voltage to the gate electrode. An impedance adjustment circuit is connected between the gate electrode and the gate drive line. A characteristic impedance of the gate electrode is Z1, when a connecting point between the impedance adjustment circuit and the gate electrode is viewed from the impedance adjustment circuit. A characteristic impedance of the gate drive line is Z2, when a connecting point between the impedance adjustment circuit and the gate drive line is viewed from the impedance adjustment circuit. X that denotes a characteristic impedance of the impedance adjustment circuit is a value between Z1 and Z2.

Integrated circuit dies having multi-gate, non-planar transistors built into a back-end-of-line portion of the die are described. In an example, non-planar transistors include an amorphous oxide semiconductor (AOS) channel extending between a source module and a drain module. A gate module may extend around the AOS channel to control electrical current flow between the source module and the drain module. The AOS channel may include an AOS layer having indium gallium zinc oxide.

A junction field-effect transistor (JFET) with a gate region that includes two separate sub-regions having material of different conductivity types and/or a Schottky junction that substantially suppresses gate current when the gate junction is forward-biased, as well as complementary circuits that incorporate such JFET devices.

A high-frequency transistor includes a source electrode, a drain electrode, a gate electrode, and a gate drive line that applies a voltage to the gate electrode. An impedance adjustment circuit is connected between the gate electrode and the gate drive line. A characteristic impedance of the gate electrode is Z1, when a connecting point between the impedance adjustment circuit and the gate electrode is viewed from the impedance adjustment circuit. A characteristic impedance of the gate drive line is Z2, when a connecting point between the impedance adjustment circuit and the gate drive line is viewed from the impedance adjustment circuit. X that denotes a characteristic impedance of the impedance adjustment circuit is a value between Z1 and Z2.