Mitsubishi Electric Corporation

Hideyuki Hatta

Shiro Hino

Yutaka Fukui

Katsutoshi Sugawara

Koji Sadamatsu

Yuichi Nagahisa

Rina Tanaka

Kotaro Kawahara

Yusuke Miyata

Kohei Adachi

Hidenori Koketsu

Naruhisa Miura

Kohei Ebihara

Shingo Tomohisa

A silicon carbide semiconductor device includes: a body region of a second conductivity type provided on a drift layer of a first conductivity type; a source region of a first conductivity type provided on the body region; a source electrode connected to the source region; a gate insulating film provided on an inner surface of a trench; a gate electrode provided inside the trench with interposition of the gate insulating film; a protective layer of a second conductivity type provided below the gate insulating film; a connection layer of a second conductivity type being in contact with the protective layer and the body region; and an electric field relaxation layer of a second conductivity type being in contact with a bottom surface of the connection layer, provided below the connection layer, and having a lower impurity concentration of a second conductivity type than the connection layer.

Silicon carbide semiconductor device, power conversion apparatus, and method for manufacturing silicon carbide semiconductor device

The present invention relates to a semiconductor device having trench gates. The semiconductor device includes the following: a first semiconductor layer; a first semiconductor region selectively disposed in the upper layer of the first semiconductor layer; a second semiconductor region in contact with the first semiconductor region; a third semiconductor region on the bottom surfaces of the first and second semiconductor regions; gate trenches provided to penetrate the first and third semiconductor regions in the thickness direction of the first and third semiconductor regions to reach the inside of the first semiconductor layer; a field-reducing region on the bottom of each gate trench; and connection layers arranged in the first semiconductor layer at intervals so as to be each in contact with at least one of sidewalls of the gate trenches, the connection layers each electrically connecting the field-reducing region to the third semiconductor region.

Semiconductor device and power converter

An object of the present invention is to suppress the passage of bipolar current in a silicon carbide semiconductor device by reducing a voltage applied to a terminal well region during reflux operations. An SiC-MOSFET includes a plurality of first well regions, a second well region, a third well region in a surface layer of a drift layer, the first, second, and third well regions being of a second conductivity type. The third well region is provided on the side of the second well region opposite to the first well regions. A unit cell that includes the first well regions includes a unipolar diode. The SiC-MOSFET includes a source electrode connected to the unipolar diode and the ohmic electrode and not having ohmic connection with the second well region and the third well region.

Silicon carbide semiconductor device and power converter

An object is to provide a technique capable of reducing a parasitic capacitance in a semiconductor device with high accuracy. A semiconductor device includes: a base region; a source region; a second trench passing through the base region to reach the drift layer; a second protective layer disposed in a bottom portion of the second trench; a source electrode, at least part of which is disposed in the second trench, to be electrically connected to a first protective layer, the base region, and the source region; and a source side connection layer of a second conductivity type constituting at least part of a lateral portion of the second trench and connected to the base region and the second protective layer.

Semiconductor device

The present invention relates to a silicon carbide semiconductor device that includes a Schottky barrier diode in a field-effect transistor and includes a first trench provided through first and second semiconductor regions in a thickness direction and reaches inside a semiconductor layer, a second trench provided through the second semiconductor region in the thickness direction and reaches inside the semiconductor layer, a gate electrode embedded in the first trench via a gate insulating film, a Schottky barrier diode electrode embedded in the second trench, a first low-resistance layer having contact with a trench side wall of the first trench, and a second low-resistance layer having contact with a trench side wall of the second trench. The second low-resistance layer has an impurity concentration that is higher than the impurity concentration in the semiconductor layer and lower than the impurity concentration in the first low-resistance layer.

A drift layer is made of silicon carbide and has a first conductivity type. At least one trench has a first side surface facing a Schottky barrier diode region, and a second side surface extending in a transistor region and contacting a source region, a body region, and the drift layer. A first protective region is provided under the at least one trench, has a second conductivity type, and is higher in impurity concentration of the second conductivity type than the body region. A second protective region extends from the first protective region, reaches at least one of the first side surface and an end region of the second side surface continuous with the first side surface, has an uppermost portion shallower than a lowermost portion of the body region, and is higher in impurity concentration of the second conductivity type than the body region.

Silicon carbide semiconductor device and method of manufacturing same

In an SiC-MOSFET with a built-in Schottky diode, a bipolar current may be passed in a second well region formed at a terminal part to reduce the breakdown voltage of the terminal part. In the SiC-MOSFET with the built-in Schottky diode, a source electrode forming non-ohmic connection such as Schottky connection with the second well region is provided on the second well region formed below a gate pad in the terminal part. By the absence of ohmic connection between the second well region and the source electrode, reduction in breakdown voltage is suppressed at the terminal part.

In an SiC-MOSFET with a built-in Schottky diode, a bipolar current may be passed in a second well region formed at a terminal part to reduce a breakdown voltage. In the SiC-MOSFET with the built-in Schottky diode, a conductive layer in Schottky connection with the second well region is provided on the second well region in the terminal part, and the conductive layer is electrically connected with a source electrode of the MOSFET. A conductive layer contact hole is provided for connecting only the conductive layer and the source electrode.

Silicon carbide semiconductor device having a conductive layer formed above a bottom surface of a well region so as not to be in ohmic connection with the well region and power converter including the same

A drift layer is formed of silicon carbide and has a first conductivity type. A trench bottom protective layer is provided on a bottom portion of a gate trench and has a second conductivity type. A depletion suppressing layer is provided between a side surface of the gate trench and the drift layer, extends from a lower portion of a body region up to a position deeper than the bottom portion of the gate trench, has the first conductivity type, and has an impurity concentration of the first conductivity type higher than that of the drift layer. The impurity concentration of the first conductivity type of the depletion suppressing layer is reduced as the distance from the side surface of the gate trench becomes larger.

Silicon carbide semiconductor device, power converter, method of manufacturing silicon carbide semiconductor device, and method of manufacturing power converter

In SiC-MOSFETs including Schottky diodes, passage of a bipolar current to a second well region formed in a terminal portion sometimes reduces a breakdown voltage. In a SiC-MOSFET including Schottky diodes according to the present invention, the second well region formed in the terminal portion has a non-ohmic connection to a source electrode, and a field limiting layer lower in impurity concentration than the second well region is formed in a surface layer area of the second well region which is a region facing a gate electrode through a gate insulating film.

A silicon carbide semiconductor device includes a diffusion protective layer provided below a gate insulating film, a gate line provided on an insulation film on the bottom face of a terminal trench and electrically connected to a gate electrode, the terminal trench being located more toward the outer side than the gate trench, a gate pad joined to the gate line in the terminal trench, a terminal protective layer provided below the insulation film on the bottom face of the terminal trench, and a source electrode electrically connected to a source region, the diffusion protective layer, and the terminal protective layer. The diffusion protective layer has first extensions that extend toward the terminal protective layer and that are separated from the terminal protective layer. This configuration inhibits an excessive electric field from being applied to the gate insulating film provided on the bottom face of the gate trench.

In SiC-MOSFETs including Schottky diodes, passage of a bipolar current to a well region in a terminal region cannot be sufficiently reduced, which may reduce the reliability of elements. A SiC-MOSFET including Schottky diodes includes a gate electrode formed, through a second insulating film thicker than a gate insulating film in an active region, on a separation region between a first well region in the active region that is the closest to the terminal region and a second well region in the terminal region, wherein the second well region has a non-ohmic connection to a source electrode. Thus, a decrease in the reliability of elements is prevented.

A drift layer has a first conductivity type. A well region has a second conductivity type. A well contact region has a resistivity lower than that of the well region. A source contact region is provided on the well region, separated from the drift layer by the well region, and has the first conductivity type. A source resistance region is provided on the well region, separated from the drift layer by the well region, is adjacent to the source contact region, has the first conductivity type, and has a sheet resistance higher than that of the source contact region. A source electrode contacts the source contact region, the well contact region, and the source resistance region, and is continuous with the channel at least through the source resistance region.

A drift layer made of silicon carbide has a first conductivity type. A body region on the drift layer has a second conductivity type. A source region on the body region has the first conductivity type. A gate insulating film is on each inner wall of at least one trench. A protective layer has at least a portion below the trench, is in contact with the drift layer, and has the second conductivity type. A first low-resistance layer is in contact with the trench and the protective layer, straddles a border between the trench and the protective layer in the depth direction, has the first conductivity type, and has a higher impurity concentration than the drift layer. A second low-resistance layer is in contact with the first low-resistance layer, is away from the trench, has the first conductivity type, and has a higher impurity concentration than the first low-resistance layer.

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Tokyo, Japan

Hideyuki Hatta