Power semiconductor device module

A power semiconductor device module, comprising:

• a base plate;
• an insulating substrate mounted on said base plate;
• and
• a power semiconductor device mounted on said insulating substrate,
• said device module being obtained by modularizing said base plate, said insulating substrate, and a power semiconductor device, wherein
• said insulating substrate has a first electrode layer disposed on a first main surface and a second electrode layer disposed on a second main surface,
• said power semiconductor device is joined onto said first electrode layer,
• said second electrode layer is joined onto a first main surface of said base plate, and
• a thermal resistance reducing section that reduces thermal resistance is provided in said second electrode layer or said base plate of a portion corresponding to a place immediately below the power semiconductor device.