Semiconductor device having a switching element and a diode connected in antiparallel

A semiconductor device comprising:

• a semiconductor module that includes a switching element and a diode connected in antiparallel to each other;
• a cooling member that cools the semiconductor module;
• and
• a heat transfer member that is disposed between the semiconductor module and the cooling member to transfer heat generated by the switching element and the diode to the cooling member,
• the heat transfer member having a mounting surface on which the switching element and the diode are mounted side by side and a surface which is located opposite to the mounting surface and disposed in contact with the cooling member, and
• in the heat transfer member, the thermal conductivity in a first direction parallel to the mounting surface being higher than the thermal conductivity in a second direction perpendicular to the mounting surface,
• wherein the thickness of the heat transfer member in the second direction is set based on a relationship between the thickness and a temperature difference between a temperature of the mounting surface of the heat transfer member and a surface temperature of the cooling member, the relationship being derived from a thermal network model for a ladder-type resistor circuit composed of thermal resistors in the first direction and thermal resistors in the second direction.