Semiconductor device and method for controlling same

A semiconductor device, comprising:

• a semiconductor part;
• a first electrode provided on a back surface of the semiconductor part;
• a second electrode provided on a front surface of the semiconductor part;
• and
• a control electrode provided between the first electrode and the second electrode, the control electrode extending into the semiconductor part from the front surface side, the control electrode being electrically insulated from the semiconductor part by a first insulating film and electrically insulated from the second electrode by a second insulating film,
• the semiconductor part including a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type, and a third semiconductor layer of the second conductivity type,
• the first semiconductor layer extending between the first and second electrodes, the control electrode extending into the first semiconductor layer from the front surface side of the semiconductor part,
• the second semiconductor layer being provided between the first semiconductor layer and the second electrode, the second semiconductor layer being connected to the second electrode,
• the third semiconductor layer being provided between the second semiconductor layer and the control electrode, the third semiconductor layer contacting the first insulating film and the second semiconductor layer, the third semiconductor layer including a second-conductivity-type impurity with a higher concentration than a concentration of a second-conductivity-type impurity in the second semiconductor layer, the third semiconductor layer contacting the second electrode and being electrically connected to the second electrode
• the third semiconductor layer having a first length in a first direction directed from the first electrode toward the second electrode, the third semiconductor layer having a first layer thickness in a second direction directed from the second semiconductor layer toward the control electrode, the first length being greater than the first layer thickness.