Semiconductor device and method of manufacturing the same

A semiconductor device comprising:

• a substrate of a first conductivity type;
• a first buried layer of a second conductivity type formed in a device formation region on the substrate;
• a second buried layer of the first conductivity type formed on the first buried layer;
• an epitaxial layer of the second conductivity type formed on the second buried layer;
• a first diffusion region of the first conductivity type that are formed on the second buried layer and surround the epitaxial layer;
• a second diffusion region of the first conductive type, at least a part of which is formed on the first diffusion region;
• a third diffusion region of the first conductivity type formed on the second diffusion region;
• a first electrode formed on the third diffusion region;
• a fourth diffusion region of the second conductivity type, at least a part of which is formed in the epitaxial layer;
• a fifth diffusion region of the first conductivity type and a sixth diffusion region of the second conductivity type formed on the fourth diffusion region;
• a second electrode formed on the fifth diffusion region and the sixth diffusion region;
• a third electrode formed above the epitaxial layer and short-circuited with the fifth diffusion region and the sixth diffusion region via the second electrode;
• and
• a semiconductor region of the second conductivity type formed to surround the first diffusion region and formed to extend from the first buried layer to a surface of the device formation region, wherein
• voltage is applied from a surface of the semiconductor region to the first buried layer to set potential of the first buried layer higher than potential of the substrate and the second buried layer.

A method of manufacturing a semiconductor device, comprising:

• sequentially laminating, on a substrate of a first conductivity type, a first buried layer of a second conductivity type, a second buried layer of the first conductivity type, an epitaxial layer of the second conductivity type;
• forming a seventh diffusion region of the second conductivity type in a center of the epitaxial layer on the second buried layer and forming a first diffusion region of the first conductivity type on the second buried layer to surround the epitaxial layer;
• forming a second diffusion region of the first conductivity type such that at least a part thereof is arranged on the first diffusion region;
• forming a third diffusion region of the first conductivity type on the second diffusion region;
• forming a fourth diffusion region of the second conductivity type in the epitaxial layer and the seventh diffusion region to extend over both the epitaxial layer and the seventh diffusion region;
• forming a third diffusion region of the first conductivity type on the second diffusion region and forming a fifth diffusion region of the first conductivity type and a sixth diffusion region of the second conductivity type on the fourth diffusion region;
• forming a first electrode on the third diffusion region and forming second electrodes on the fifth diffusion region and the sixth diffusion region;
• forming a third electrode above the epitaxial layer and short-circuiting the third electrode and the fifth and sixth diffusion regions via the second electrodes;
• and
• keeping the first buried layer in a floating state.