Semiconductor device comprising a mosfet having a resurf region and higher peak impurity concentration diffusion region in the resurf region

A semiconductor device comprising:

• a semiconductor substrate formed with a first region of a first conductivity type;
• a second region that is a RESURF region of a second conductivity type formed in a surface portion of the first region to separate a high-side circuit and a low-side circuit from each other;
• a third region of the second conductivity type formed at least in a bottom portion of the second region close to the high-side circuit, having a higher peak concentration of impurities than the second region;
• and
• a MOSFET using the second region as a drift layer,
• the MOSFET including:
• a fourth region serving as a drain region of the second conductivity type formed in the surface portion of the second region, having a higher peak concentration of impurities than the second region;
• a sixth region serving as a source region of the second conductivity type formed in a surface portion of a fifth region of the first conductivity type or in a surface portion of the first region, in a region closer to the low-side circuit than the fourth region, the fifth region being provided in the second region;
• a first thermal oxide film formed on a surface of the second region, in a region between the fourth region and the sixth region;
• and
• a seventh region of the second conductivity type formed in a surface portion of the second region below the first thermal oxide film, having a higher peak concentration of impurities than the second region,
• wherein an end portion of the seventh region close to the low-side circuit is located closer to the low-side circuit than an end portion of the third region close to the low-side circuit,
• the semiconductor device further comprising:
• a second thermal oxide film formed on the surface of the second region, closer to the high-side circuit than the fourth region;
• and
• an eighth region of the second conductivity type formed below the second thermal oxide film, having a higher peak concentration of impurities than the second region, and
• when the eighth region has an impurity concentration indicated as N1 and the seventh region has an impurity concentration indicated as N2, a relationship, 0.1×N1<N2<2×N1, is satisfied.

A semiconductor device comprising:

• a semiconductor substrate formed with a first region of a first conductivity type;
• a second region that is a RESURF region of a second conductivity type formed in a surface portion of the first region to separate a high-side circuit and a low-side circuit from each other;
• a third region of the second conductivity type formed at least in a bottom portion of the second region close to the high-side circuit, having a higher peak concentration of impurities than the second region;
• and
• a MOSFET using the second region as a drift layer,
• the MOSFET including:
• a fourth region serving as a drain region of the second conductivity type formed in the surface portion of the second region, having a higher peak concentration of impurities than the second region;
• a sixth region serving as a source region of the second conductivity type formed in a surface portion of a fifth region of the first conductivity type or in a surface portion of the first region, in a region closer to the low-side circuit than the fourth region, the fifth region being provided in the second region;
• a first thermal oxide film formed on a surface of the second region, in a region between the fourth region and the sixth region;
• and
• a seventh region of the second conductivity type formed in a surface portion of the second region below the first thermal oxide film, having a higher peak concentration of impurities than the second region,
• wherein an end portion of the seventh region close to the low-side circuit is located closer to the low-side circuit than an end portion of the third region close to the low-side circuit, and
• the semiconductor device further comprising:
• a ninth region of the second conductivity type formed in a region closer to the low-side circuit than the seventh region, having a peak concentration of impurities lower than the seventh region and higher than the second region.

A semiconductor device comprising:

• a semiconductor substrate formed with a first region of a first conductivity type;
• a second region that is a RESURF region of a second conductivity type formed in a surface portion of the first region to separate a high-side circuit and a low-side circuit from each other;
• a third region of the second conductivity type formed at least in a bottom portion of the second region close to the high-side circuit, having a higher peak concentration of impurities than the second region;
• and
• a MOSFET using the second region as a drift layer,
• the MOSFET including:
• a fourth region serving as a drain region of the second conductivity type formed in the surface portion of the second region, having a higher peak concentration of impurities than the second region;
• a sixth region serving as a source region of the second conductivity type formed in a surface portion of a fifth region of the first conductivity type or in a surface portion of the first region, in a region closer to the low-side circuit than the fourth region, the fifth region being provided in the second region;
• a first thermal oxide film formed on a surface of the second region, in a region between the fourth region and the sixth region;
• and
• a seventh region of the second conductivity type formed in a surface portion of the second region below the first thermal oxide film, having a higher peak concentration of impurities than the second region,
• wherein an end portion of the seventh region close to the low-side circuit is located closer to the low-side circuit than an end portion of the third region close to the low-side circuit, and
• the semiconductor device further comprising:
• a ninth region of the second conductivity type formed discretely in a region closer to the low-side circuit than the seventh region, having a peak concentration of impurities equal to or lower than the seventh region and higher than the second region.

A semiconductor device comprising:

• a semiconductor substrate formed with a first region of a first conductivity type;
• a second region that is a RESURF region of a second conductivity type formed in a surface portion of the first region to separate a high-side circuit and a low-side circuit from each other;
• a third region of the second conductivity type formed at least in a bottom portion of the second region close to the high-side circuit, having a higher peak concentration of impurities than the second region;
• and
• a MOSFET using the second region as a drift layer,
• the MOSFET including:
• a fourth region serving as a drain region of the second conductivity type formed in the surface portion of the second region, having a higher peak concentration of impurities than the second region;
• a sixth region serving as a source region of the second conductivity type formed in a surface portion of a fifth region of the first conductivity type or in a surface portion of the first region, in a region closer to the low-side circuit than the fourth region, the fifth region being provided in the second region;
• a first thermal oxide film formed on a surface of the second region, in a region between the fourth region and the sixth region;
• and
• a seventh region of the second conductivity type formed in a surface portion of the second region below the first thermal oxide film, having a higher peak concentration of impurities than the second region,
• wherein an end portion of the seventh region close to the low-side circuit is located closer to the low-side circuit than an end portion of the third region close to the low-side circuit, and
• the seventh region includes a portion close to the low-side circuit, having an impurity concentration higher than a portion close to the high-side circuit.

A semiconductor device comprising:

• a semiconductor substrate formed with a first region of a first conductivity type;
• a second region that is a RESURF region of a second conductivity type formed in a surface portion of the first region to separate a high-side circuit and a low-side circuit from each other;
• a third region of the second conductivity type formed at least in a bottom portion of the second region close to the high-side circuit, having a higher peak concentration of impurities than the second region;
• and
• a MOSFET using the second region as a drift layer,
• the MOSFET including:
• a fourth region serving as a drain region of the second conductivity type formed in the surface portion of the second region, having a higher peak concentration of impurities than the second region;
• a sixth region serving as a source region of the second conductivity type formed in a surface portion of a fifth region of the first conductivity type or in a surface portion of the first region, in a region closer to the low-side circuit than the fourth region, the fifth region being provided in the second region;
• a first thermal oxide film formed on a surface of the second region, in a region between the fourth region and the sixth region;
• and
• a seventh region of the second conductivity type formed in a surface portion of the second region below the first thermal oxide film, having a higher peak concentration of impurities than the second region,
• wherein an end portion of the seventh region close to the low-side circuit is located closer to the low-side circuit than an end portion of the third region close to the low-side circuit,
• the semiconductor device further comprising:
• a polysilicon layer formed on an end portion of the first thermal oxide film close to the high-side circuit, and
• an end portion of the polysilicon layer close to the low-side circuit is located closer to the low-side circuit than an end portion of the seventh region close to the low-side circuit.