Mosfet

A MOSFET used in a power conversion circuit which includes a power source and the MOSFET for controlling an electric current supplied from the power source, wherein

• the MOSFET includes a semiconductor base substrate having an n-type column region and a p-type column region, the n-type column region and the p-type column region forming a super junction structure,
• a total amount of a dopant in the p-type column region is set to a value which falls within a range of 1.00 to 1.03 times as much as a total amount of a dopant in the n-type column region, and
• the MOSFET is configured to be operated during a period from a point of time when a drain current starts to decrease to a point of time when the drain current becomes 0 for the first time in response to turning off of the MOSFET such that a first period during which the drain current is decreased, a second period during which the drain current is increased or the drain current becomes constant, and a third period during which the drain current is decreased again occur in this order.