Semiconductor device and method for manufacturing semicondcutor device

A semiconductor device comprising:

• a first conductivity type first semiconductor layer;
• a second conductivity type second semiconductor layer on the first semiconductor layer;
• an MIS transistor structure defined in a surface portion on the side of the second semiconductor layer opposite to the first semiconductor layer;
• a trench defined selectively in the first semiconductor layer and having a bottom portion reaching the second semiconductor layer;
• and
• a first electrode defined on a back surface of the first semiconductor layer such that the first electrode enters the trench, wherein
• the second semiconductor layer has a second conductivity type region in a manner extending across a first portion exposed at the bottom portion of the trench and a second portion in contact with the first conductivity type layer, and
• the first electrode is in Ohmic contact with the second conductivity type region at least at the bottom portion of the trench and in Ohmic contact with the first semiconductor layer, and
• the second conductivity type region has a carrier lifetime of equal to or longer than 0.1 μs.

A semiconductor device manufacturing method comprising the steps of:

• defining a second conductivity type second semiconductor layer on one of the surfaces of a first conductivity type first semiconductor layer;
• defining an MIS transistor structure in a surface portion on the side of the second semiconductor layer opposite to the first semiconductor layer;
• selectively etching the other surface of the first semiconductor layer opposite to the second semiconductor layer to define a trench having a bottom portion reaching the second semiconductor layer;
• and
• defining a first electrode to be in Ohmic contact with the second conductivity type region of the second semiconductor layer at least at the bottom portion of the trench and in Ohmic contact with the first semiconductor layer on the other surface of the first semiconductor layer so as to enter the trench.

A semiconductor device comprising:

• a first conductivity type first semiconductor layer formed by epitaxial growth;
• a second conductivity type second semiconductor layer formed on the first semiconductor layer by epitaxial growth;
• an MIS transistor structure defined in a surface portion on the side of the second semiconductor layer opposite to the first semiconductor layer;
• a trench defined selectively in the first semiconductor layer and having a bottom portion reaching the second semiconductor layer;
• and
• a first electrode defined on a back surface of the first semiconductor layer such that the first electrode enters the trench, wherein
• the second semiconductor layer has a second conductivity type region in a manner extending across a first portion exposed at the bottom portion of the trench and a second portion in contact with the first conductivity type layer, and
• the first electrode is in Ohmic contact with the second conductivity type region at least at the bottom portion of the trench and in Ohmic contact with the first semiconductor layer.