An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

A power semiconductor device includes trenches disposed in a first base layer of a first conductivity type at intervals to partition main and dummy cells, at a position remote from a collector layer of a second conductivity type. In the main cell, a second base layer of the second conductivity type, and an emitter layer of the first conductivity type are disposed. In the dummy cell, a buffer layer of the second conductivity type is disposed. A gate electrode is disposed, through a gate insulating film, in a trench adjacent to the main cell. A buffer resistor having an infinitely large resistance value is inserted between the buffer layer and emitter electrode. The dummy cell is provided with an inhibiting structure to reduce carriers of the second conductivity type to flow to and accumulate in the buffer layer from the collector layer.

Power semiconductor device

Recent success with the fabrication of high-performance GaN-on-Si high-voltage HFETs has made this technology a contender for power electronic applications. This paper discusses the properties of GaN that make it an attractive alternative to established silicon and emerging SiC power devices. Progress in development of vertical power devices from bulk GaN is reviewed followed by analysis of the prospects for GaN-on-Si HFET structures. Challenges and innovative solutions to creating enhancement-mode power switches are reviewed.

https://iopscience.iop.org/article/10.1088/0268-1242/28/7/074011/pdf

Gallium nitride devices for power electronic applications

In this paper, GaN power transistors on Si substrates for power switching application are reported. GaN heterojunction field-effect transistor (HFET) structure on Si is an important configuration in order to realize a low loss and high power devices as well as one of the cost-effective solutions. Current collapse phenomena are discussed for GaN-HFETs on Si substrate, resulting in suppression of the current collapse due to using the conducting Si substrate. Furthermore, attempts for normally off GaN-FETs were examined. A hybrid metal-oxide-semiconductor HFET structure is a promising candidate for obtaining devices with a lower on-resistance (Ron) and a high breakdown voltage (Vb).

GaN Power Transistors on Si Substrates for Switching Applications

In this paper, GaN power transistors on Si substrates for power switching application are reported. GaN heterojunction field-effect transistor (HFET) structure on Si is an important configuration in order to realize a low loss and high power devices as well as one of the cost-effective solutions. Current collapse phenomena are discussed for GaN-HFETs on Si substrate, resulting in suppression of the current collapse due to using the conducting Si substrate. Furthermore, attempts for normally off GaN-FETs were exam- ined. A hybrid metal-oxide-semiconductor HFET structure is a promising candidate for obtaining devices with a lower on-resistance ðRonÞ and a high breakdown voltage ðVbÞ.

GaN Power Transistors on Si Substrates for Switching Applications Hybrid MOS-FET transistor devices with low on-resistance, high hold-voltages and high breakdown voltage promise to provide high-power, low-loss operation for switching applications.

A novel method for fabricating trench structures on GaN was developed. A smooth non-polar (1100) plane was obtained by wet etching using tetramethylammonium hydroxide (TMAH) as the etchant. A U-shape trench with the (1100) plane side walls was formed with dry etching and the TMAH wet etching. A U-shape trench gate metal oxide semiconductor field-effect transistor (MOSFET) was also fabricated using the novel etching technology. This device has the excellent normally-off operation of drain current–gate voltage characteristics with the threshold voltage of 10 V. The drain breakdown voltage of 180 V was obtained. The results indicate that the trench gate structure can be applied to GaN-based transistors.

https://iopscience.iop.org/article/10.1143/APEX.1.021104/pdf

GaN-Based Trench Gate Metal Oxide Semiconductor Field-Effect Transistor Fabricated with Novel Wet Etching

The silicon carbide semiconductor device includes a substrate, a drift layer, a base region, a source region, a trench, a gate insulating layer, a gate electrode, a source electrode, a drain electrode, and a deep layer. The deep layer is disposed under the base region and is located to a depth deeper than the trench. The deep layer is divided into a plurality of portions in a direction that crosses a longitudinal direction of the trench. The portions include a group of portions disposed at positions corresponding to the trench and arranged at equal intervals in the longitudinal direction of the trench. The group of portions surrounds corners of a bottom of the trench.

Silicon carbide semiconductor device and method of manufacturing the same

We fabricated a vertical insulated gate AlGaN/GaN heterojunction field-effect transistor (HFET), using a free-standing GaN substrate. This HFET has apertures through which the electron current vertically flows. These apertures were formed by dry etching the p-GaN layer below the gate electrodes and regrowing n--GaN layer without mask. The HFET exhibited a specific on-resistance of as low as 2.6 mΩ·cm2 with a threshold voltage of -16 V. This HFET would be a prototype of a GaN-based high-power switching device.

https://iopscience.iop.org/article/10.1143/JJAP.46.L503/pdf

A Vertical Insulated Gate AlGaN/GaN Heterojunction Field-Effect Transistor

DLTS study of n-type GaN grown by MOCVD on GaN substrates

The semiconductor device has a stacked structure in which a p-GaN layer 32, an SI-GaN layer 62, and an AlGaN layer 34 are stacked, and has a gate electrode 44 that is formed at a top surface side of the AlGaN layer 34. A band gap of the AlGaN layer 34 is wider than a band gap of the p-GaN layer 32 and the SI-GaN layer 62. Moreover, impurity concentration of the SI-GaN layer 62 is less than 1x1017cm-3. The semiconductor devices comprising III-V semiconductors that have a stable normally-off operation are realized.

Narumasa Soejima

Papers

GaN-Based Trench Gate Metal Oxide Semiconductor Field-Effect Transistor Fabricated with Novel Wet Etching

Silicon carbide semiconductor device and method of manufacturing the same

A Vertical Insulated Gate AlGaN/GaN Heterojunction Field-Effect Transistor

DLTS study of n-type GaN grown by MOCVD on GaN substrates

Iii-v hemt devices