Semiconductor device and power conversion device

1. A semiconductor device comprising:

a positive electrode-side semiconductor element including a first positive electrode and a first negative electrode;

a negative electrode-side semiconductor element including a second positive electrode and a second negative electrode;

a positive electrode plate connected to the first positive electrode of the positive electrode-side semiconductor element;

a negative electrode plate connected to the second negative electrode of the negative electrode-side semiconductor element;

an AC electrode plate connected to the first negative electrode of the positive electrode-side semiconductor element and the second positive electrode of the negative electrode-side semiconductor element;

a positive electrode-side auxiliary electrode terminal;

a negative electrode-side auxiliary electrode terminal;

a positive electrode-side capacitor connected to the positive electrode plate and the positive electrode-side auxiliary electrode terminal;

a negative electrode-side capacitor connected to the negative electrode plate and the negative electrode-side auxiliary electrode terminal;

a heat dissipation conductor; and

an insulator provided between the heat dissipation conductor and each of the positive electrode plate, the negative electrode plate and the AC electrode plate, wherein

a capacitance of the positive electrode-side capacitor is greater than a capacitance provided between the first positive electrode of the positive electrode-side semiconductor element and the heat dissipation conductor with the positive electrode plate interposed therebetween, and

a capacitance of the negative electrode-side capacitor is greater than a capacitance provided between the second negative electrode of the negative electrode-side semiconductor element and the heat dissipation conductor with the negative electrode plate interposed therebetween.

2. The semiconductor device according to claim 1 , further comprising an auxiliary electrode plate provided on the insulator, wherein

the negative electrode-side auxiliary electrode terminal is connected to the auxiliary electrode plate,

the negative electrode-side capacitor is disposed on the auxiliary electrode plate, and

the negative electrode plate is disposed on the negative electrode-side semiconductor element and the negative electrode-side capacitor.

3. The semiconductor device according to claim 1 , wherein

the AC electrode plate is disposed on the positive electrode-side semiconductor element,

the negative electrode-side semiconductor element is disposed on the AC electrode plate, and

the negative electrode plate is disposed on the negative electrode-side semiconductor element.

4. The semiconductor device according to claim 1 , wherein

the positive electrode-side auxiliary electrode terminal and the negative electrode-side auxiliary electrode terminal are integrated with each other to form a common auxiliary electrode terminal.

5. The semiconductor device according to claim 1 , wherein

each of the positive electrode-side capacitor and the negative electrode-side capacitor includes

a conductor, and

an insulator,

the positive electrode-side capacitor is formed by sandwiching the insulator of the positive electrode-side capacitor between the positive electrode plate and the conductor, and

the negative electrode-side capacitor is formed by sandwiching the insulator of the negative electrode-side capacitor between the negative electrode plate and the conductor.

6. The semiconductor device according to claim 1 , wherein

each of the positive electrode-side capacitor and the negative electrode-side capacitor includes

a plurality of conductors, and

a plurality of insulators that are equal in number to the plurality of conductors,

the plurality of insulators and the plurality of conductors are stacked alternately one by one sequentially in a single column on each of the positive electrode plate and the negative electrode plate,

a first conductor of the plurality of conductors stacked on the positive electrode plate in an odd-numbered layer counted from the positive electrode plate is connected to the positive electrode-side auxiliary electrode terminal, and a second conductor of the plurality of conductors stacked on the positive electrode plate in an even-numbered layer counted from the positive electrode plate is connected to the positive electrode plate, and

a third conductor of the plurality of conductors stacked on the negative electrode plate in an odd-numbered layer counted from the negative electrode plate is connected to the negative electrode-side auxiliary electrode terminal, and a fourth conductor of the plurality of conductors stacked on the negative electrode plate in an even-numbered layer counted from the negative electrode plate is connected to the negative electrode plate.

7. The semiconductor device according to claim 1 , wherein

the positive electrode-side semiconductor element is connected to one of the positive electrode plate and the AC electrode plate through a first connection conductor, and

the negative electrode-side semiconductor element is connected to one of the negative electrode plate and the AC electrode plate through a second connection conductor.

8. A power conversion device comprising:

the semiconductor device according to claim 1 ;

a load; and

a load-accommodating metal housing in which the load is accommodated,

the positive electrode-side auxiliary electrode terminal and the negative electrode-side auxiliary electrode terminal being connected to the load-accommodating metal housing.

9. The power conversion device according to claim 8 , further comprising an inductor, wherein

the load-accommodating metal housing is connected to a ground through the inductor.