Semiconductor device
A semiconductor device having a semiconductor substrate is provided, the semiconductor substrate including: two trench sections extending in a predetermined direction; a mesa section provided between the two trench sections; and a drift layer, the mesa section including: an emitter region; a contact region; and multiple accumulation layers provided side by side in a depth direction below the emitter region and the contact region, and at least one accumulation layer among the multiple accumulation layers provided below at least a part of the emitter region, but not provided below a partial region of the contact region.
1. A semiconductor device having a semiconductor substrate, the semiconductor substrate comprising:
two trench sections extending in a predetermined direction;
a mesa section provided between the two trench sections; and
a drift layer of a first conductivity type provided below the mesa section, wherein
the mesa section has:
an emitter region of a first conductivity type having a higher doping concentration than that of the drift layer, and having at least a part located on an upper surface of the semiconductor substrate;
a contact region of a second conductivity type having at least a part located on the upper surface of the semiconductor substrate; and
multiple accumulation layers provided side by side in a depth direction from the upper surface to a lower surface of the semiconductor substrate below the emitter region and the contact region, and having a doping concentration of the first conductivity type higher than a doping concentration of the first conductivity type of the drift layer, and
at least one accumulation layer among the multiple accumulation layers is provided below at least a part of the emitter region, but not provided below a partial region of the contact region.
2. The semiconductor device according to claim 1 , wherein
the emitter region and the contact region are alternately provided in the predetermined direction.
3. The semiconductor device according to claim 2 , wherein
the at least one accumulation layer is not provided below a partial region in each of a plurality of the contact regions.
4. The semiconductor device according to claim 3 , wherein
the at least one accumulation layer is an island-shaped accumulation layer that includes a plurality of accumulation regions which have a doping concentration of the first conductivity type higher than a doping concentration of the first conductivity type of the drift layer, and each of which is provided discretely in a plane orthogonal to the depth direction,
each of the plurality of accumulation regions is provided below at least a part of the emitter region, but not provided below a partial region of the contact region to be separated, and
all of the accumulation layers except an accumulation layer closest to the upper surface in the depth direction are the island-shaped accumulation layers.
5. The semiconductor device according to claim 4 , wherein
the mesa section further includes a base region having a doping concentration of the second conductivity type lower than that of the contact region,
the emitter region has, inside the semiconductor substrate, a bottom region that is not in direct contact with the contact region and that is in direct contact with the base region, and
a length of each of the plurality of accumulation regions in the predetermined direction is longer than a length of the bottom region in the predetermined direction.
6. The semiconductor device according to claim 4 , wherein
the mesa section further includes a base region having a doping concentration of the second conductivity type lower than that of the contact region,
an emitter region has, inside the semiconductor substrate, a bottom region that is not in direct contact with the contact region and that is in direct contact with the base region, and
a length of each of the plurality of accumulation regions in the predetermined direction is shorter than a length of the bottom region in the predetermined direction.
7. The semiconductor device according to claim 5 , wherein
when a length of each of the plurality of accumulation regions in the predetermined direction is defined as L CHS and a length of the bottom region of the emitter region in the predetermined direction is defined as L 0 , L CHS and L 0 satisfy an expression: 0.5≤L CHS /L 0 ≤2.
8. The semiconductor device according to claim 1 , wherein
the mesa section further has a high concentration contact region that includes an upper portion located on the upper surface of the semiconductor substrate and a lower portion that is in contact with the contact region, the high concentration contact region having a doping concentration of the second conductivity higher than that of the contact region.
9. The semiconductor device according to claim 1 , wherein
the semiconductor device comprises a transistor section, a diode section and a boundary section that is provided in a partial region in the transistor section in direct contact with the diode section, and
the diode section includes one or more accumulation layers in a depth direction from the upper surface toward the lower surface.
10. The semiconductor device according to claim 9 , wherein
the diode section includes the contact region, and
at least one accumulation layer among the multiple accumulation layers in the diode section is provided below at least a part of the contact region.
11. The semiconductor device according to claim 10 , wherein
a length of each of the multiple accumulation layers of the diode section in the predetermined direction is longer than a length of the contact region of the diode section in the predetermined direction.