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

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

PROBLEM TO BE SOLVED: To suppress the fluctuation of the current sensing ratio of a semiconductor device at an atmospheric temperature. SOLUTION: A semiconductor device forms a main region 1 in which main current flows and a sensing region 2 in which branched current flows on the same substrate, and numbers of cells in the sense cell region 2 amount to not more than 0.1% of the numbers in the main cell region. At that time, a resistant temperature coefficient of a peripheral cell existing along the boundary of the regions is equal to that of an inside cell existing away from the boundary. Otherwise, the ratio of the numbers of the peripheral cell and the inside cell is equal in the main region 1 and the sensing region 2. COPYRIGHT: (C)2005,JPO&NCIPI

Semiconductor device having current sensing function

This paper presents a new 3D lateral power MOSFET which has a double gate and a trench gate/drain structure. The double gate structure decreased its channel resistance, and the trench gate/drain structure decreased its n drift resistance. We realized this structure using solid phase epitaxy and a conventional trench technology. From experimental results, a breakdown voltage of 49.5 V and a specific on-resistance of 42 m/spl Omega//spl middot/mm/sup 2/ were obtained.

New 3-D lateral power MOSFETs with ultra low on-resistance

PROBLEM TO BE SOLVED: To provide a group III nitride semiconductor device having a trench or mesa-structure, in which leak of a current and a decrease in withstand voltage are prevented. SOLUTION: A GaN layer 2 is grown on a C-face sapphire substrate 1, and a T-shaped USG film 3 is fabricated on the GaN layer 2 so that the side surface of the USG film 3 is parallel to an A-face and an M-face of the GaN layer 2. After that, the GaN layer 2 is dry-etched using the USG film 3 as a mask. Fig.2a and 2b show that the M-face has less roughness than the A-face. Subsequently, the GaN layer 2 is wet-etched with a TMAH solution. Fig.2c and 2d show that the roughness on the A-face and M-face are eliminated, and especially, the M-face has a mirror surface. Thus, where a trench groove side surface or a mesa-etching side surface is used as the M-face, the leak current and decrease in withstand voltage of the group III nitride semiconductor device can be prevented. COPYRIGHT: (C)2008,JPO&INPIT

Eiko Hayashi

Papers

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

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

Semiconductor device having current sensing function

New 3-D lateral power MOSFETs with ultra low on-resistance

Group iii nitride semiconductor device having trench or mesa-structure, and manufacturing method thereof