Semiconductor device

A semiconductor device comprising:

• a first substrate including a first insulating substrate, a first wiring pattern layer and a plurality of first front-side pads formed on a front surface of the first insulating substrate, and a first base portion constituted by thick copper and formed on a back surface of the first insulating substrate, wherein a first opening reaching a front surface of the first base portion from the front surface is formed in the first insulating substrate;
• a first semiconductor element mounted and fixed on the front surface of the first base portion of the first substrate via a first heat sink in the first opening of the first substrate, and electrically connected to a line constituting the first wiring pattern layer of the first substrate;
• a second substrate including a second insulating substrate, a second wiring pattern layer and a plurality of second front-side pads formed on a front surface of the second insulating substrate, and a second base portion constituted by thick copper and formed on a back surface of the second insulating substrate, wherein a second opening reaching a front surface of the second base portion from the front surface is formed in the second insulating substrate;
• a second semiconductor element mounted and fixed on the front surface of the second base portion of the second substrate via a second heat sink in the second opening of the second substrate, and electrically connected to a line constituting the second wiring pattern layer of the second substrate;
• and
• a third substrate arranged between the first substrate and the second substrate in such a manner as to face the first substrate and the second substrate, the third substrate including a plurality of third back-side pads on a back surface thereof, each of the third back-side pads being connected to a corresponding one of the plurality of first front-side pads of the first substrate by a connection member, and a plurality of third front-side pads on a front surface thereof, each of the third front-side pads being connected to each of the plurality of second front-side pads of the second substrate by a connection member.