Silicon carbide semiconductor device and manufacturing method thereof

A silicon carbide semiconductor device comprising:

• a semiconductor substrate made up of a low-resistance semiconductor layer of a first conductive type, a high-resistance semiconductor layer of the first conductive type and a first semiconductor layer of a second conductive type;
• a semiconductor region of the first conductive type formed in a predetermined region of a surface of the first semiconductor layer;
• a trench passing from a surface of the semiconductor substrate through the semiconductor region and the first semiconductor layer;
• a second semiconductor layer of the first conductive type consisting of a thin film of silicon carbide formed at least on a surface of the first semiconductor layer at a side face of the trench;
• a gate insulating film formed at least on a surface of the second semiconductor layer;
• a gate electrode layer of the second conductive type formed on the gate insulating film in the trench;
• a first electrode layer formed at least on a surface of a part of the semiconductor region at the surface of the semiconductor substrate;
• and
• a second electrode layer formed on a rear side of the semiconductor substrate,
• wherein a film thickness X(.mu.m) and an impurity concentration N(cm.sup.-3) of the second semiconductor layer with respect to a withstand voltage Y(V) thereof satisfy the relationship Y<-10000{(X-0.8)+0.3(logN-15)}.

A silicon carbide semiconductor device comprising:

• a semiconductor substrate made up of a low-resistance semiconductor layer of a first conductive type, a high-resistance semiconductor layer of the first conductive type and a first semiconductor layer of a second conductive type;
• a semiconductor region of the first conductive type formed in a predetermined region of a surface of the first semiconductor layer;
• a trench passing from a surface of the semiconductor substrate through the semiconductor region and the first semiconductor layer;
• a second semiconductor layer of the first conductive type consisting of a thin film of silicon carbide formed at least on a surface of the first semiconductor layer at a side face of the trench;
• a gate insulating film formed at least on a surface of the second semiconductor layer;
• a gate electrode layer of the first conductive type formed on the gate insulating film in the trench;
• a first electrode layer formed at least on a surface of a part of the semiconductor region at the surface of the semiconductor substrate;
• and
• a second electrode layer formed on a rear side of the semiconductor substrate,
• wherein a film thickness X(.mu.m) and an impurity concentration N(cm.sup.-3) of the second semiconductor layer with respect to a withstand voltage Y(V) thereof satisfy the relationship Y<-10000{(X-0.6)+0.3(logN-15)}.

A silicon carbide semiconductor device comprising:

• a semiconductor substrate consisting of hexagonal system monocrystalline silicon carbide and made up of a low-resistance semiconductor layer of a first conductive type, a high-resistance semiconductor layer of the first conductive type and a first semiconductor layer of a second conductive type;
• a semiconductor region of the first conductive type formed in a predetermined region of a surface of the first semiconductor layer;
• a trench passing from a surface of the semiconductor substrate through the semiconductor region and the first semiconductor layer and reaching the high-resistance semiconductor layer and having a side face substantially parallel with a [1100] direction;
• a second semiconductor layer consisting of a thin film of silicon carbide formed at least on a surface of the first semiconductor layer at a side face of the trench;
• a gate insulating film formed at least on a surface of the second semiconductor layer;
• a gate electrode layer formed on the gate insulating film in the trench;
• a first electrode layer formed at least on a part of the semiconductor region at the surface of the semiconductor substrate;
• and
• a second electrode layer formed on a rear side of the semiconductor substrate.

A silicon carbide semiconductor device comprising:

• a semiconductor substrate consisting of silicon carbide and made up of a low-resistance semiconductor layer of a first conductive type, a high-resistance semiconductor layer of the first conductive type and a first semiconductor layer of a second conductive type;
• a semiconductor region of the first conductive type formed in a predetermined region of a surface of the first semiconductor layer;
• a trench passing from a surface of the semiconductor substrate through the semiconductor region and the first semiconductor layer;
• a second semiconductor layer consisting of a thin film of silicon carbide formed at least on a surface of the first semiconductor layer at a side face of the trench;
• a gate oxide film formed at least on a surface of the second semiconductor layer;
• a gate electrode layer formed on the gate oxide film in the trench;
• a first electrode layer formed at least on a surface of a part of the semiconductor region at the surface of the semiconductor substrate;
• and
• a second electrode layer formed on a rear side of the semiconductor substrate,
• wherein when a reverse bias voltage is impressed on a pn junction between the first electrode layer and the second electrode layer a pn junction between the high-resistance semiconductor layer of the first conductive type and the first semiconductor layer of the second conductive type becomes conductive before a surface of the gate oxide film at a bottom of the trench undergoes avalanche breakdown.

A silicon carbide semiconductor device comprising:

• a semiconductor substrate consisting of silicon carbide and made up of a first low-resistance semiconductor layer of a first conductive type, a high-resistance semiconductor layer of the first conductive type, a second low-resistance semiconductor layer of the first conductive type and a first semiconductor layer of a second conductive type;
• a semiconductor region of the first conductive type formed in a predetermined region of a surface of the first semiconductor layer;
• a trench passing from a surface of the semiconductor substrate through the semiconductor region and the first semiconductor layer and reaching at least the second low-resistance semiconductor layer;
• a second semiconductor layer consisting of a thin film of silicon carbide formed at least on a surface of the first semiconductor layer at a side face of the trench;
• a gate oxide film formed at least on a surface of the second semiconductor layer;
• a gate electrode layer formed on the gate oxide film in the trench;
• a first electrode layer formed at least on a surface of a part of the semiconductor region at the surface of the semiconductor substrate;
• and
• a second electrode layer formed on a rear side of the semiconductor substrate.

A silicon carbide semiconductor device comprising:

• a semiconductor substrate consisting of silicon carbide and made up of a low-resistance semiconductor layer of a first conductive type, a high-resistance semiconductor layer of the first conductive type and a first semiconductor layer of a second conductive type;
• a semiconductor region of the first conductive type formed in a predetermined region of a surface of the first semiconductor layer;
• a trench passing from a surface of the semiconductor substrate through the semiconductor region and the first semiconductor layer;
• a second semiconductor layer consisting of a thin film of silicon carbide formed at least on a surface of the first semiconductor layer at a side face of the trench;
• a gate oxide film formed at least on a surface of the second semiconductor layer;
• a gate electrode layer formed on the gate oxide film in the trench;
• a first electrode layer formed at least on a surface of a part of the semiconductor region at the surface of the semiconductor substrate;
• and
• a second electrode layer formed on a rear side of the semiconductor substrate,
• wherein the high-resistance semiconductor layer is set to a thickness such that, when a reverse bias voltage is impressed on a pn junction between the first electrode layer and the second electrode layer and a pn junction between the high-resistance semiconductor layer and the first semiconductor layer has become conductive, a depletion layer extending from the gate oxide film toward the low-resistance semiconductor layer does not reach the low-resistance semiconductor layer.

A silicon carbide semiconductor device comprising:

• a semiconductor substrate consisting of silicon carbide and made up of a low-resistance semiconductor layer of a first conductive type, a high-resistance semiconductor layer of the first conductive type and a first semiconductor layer of a second conductive type;
• a semiconductor region of the first conductive type formed in a predetermined region of a surface of the first semiconductor layer;
• a trench passing from a surface of the semiconductor substrate through the semiconductor region and the first semiconductor layer;
• a second semiconductor layer consisting of a thin film of silicon carbide formed at least on a surface of the first semiconductor layer at a side face of the trench;
• a gate oxide film formed at least on a surface of the second semiconductor layer;
• a gate electrode layer formed on the gate oxide film in the trench;
• a first electrode layer formed at least on a surface of a part of the semiconductor region at the surface of the semiconductor substrate;
• a second electrode layer formed on a rear side of the semiconductor substrate;
• and
• an embedded semiconductor layer formed in the high-resistance semiconductor layer to be away from the trench and in contact with the first semiconductor layer.