Silicon carbide semiconductor device with cell section and outer periphery section

A silicon carbide semiconductor device comprising:

• a cell section;
• and
• an outer peripheral section including a guard ring section surrounding an outer periphery of the cell section, wherein:
• each of the cell section and the outer peripheral section includes:
• a substrate having a first conductivity type or a second conductivity type;
• a drift layer having the first conductivity type with an impurity concentration lower than the substrate, and arranged on a top surface side of the substrate;
• and
• a current dispersion layer having the first conductivity type with an impurity concentration higher than the drift layer, and arranged on the drift layer;
• the cell section further includes a vertical semiconductor element having:
• a second-conductivity-type layer arranged in the current dispersion layer with a striped pattern shape;
• a first electrode electrically connected to the second-conductivity-type layer;
• and
• a second electrode electrically connected to a back surface side of the substrate;
• the vertical semiconductor element flows a current between the first electrode and the second electrode;
• the guard ring section includes a plurality of linear guard rings having the second conductivity type with a linear frame shape, arranged to extend from a top surface of the current dispersion layer, and surrounding the cell section;
• the guard ring section includes a recessed portion provided by a concavity of the current dispersion layer deeper than the cell section, and the cell section protrudes from the guard ring section in a thickness direction of the substrate to provide a mesa portion with an island shape;
• the guard ring section further includes an electric field relaxation layer having the first conductivity type or the second conductivity type with a carrier concentration lower than the current dispersion layer and the guard rings, arranged in the current dispersion layer, and extending from a boundary position between the mesa portion and the recessed portion toward an outside of an outer periphery of the mesa portion;
• and
• an upper surface of the electric field relaxation layer is located at a position deeper than a top surface of each guard ring and shallower than a bottom surface of each guard ring.