Patent ID: 7671409

Claim:
A field-effect transistor power device comprising: a source electrode; a drain electrode; a wide gap semiconductor including a channel region and a drift region, the channel region and the drift region forming a series current path between the source electrode and the drain electrode, a gate insulating film that covers the channel region, and a gate electrode formed on the gate insulating film, wherein, in the series current path which is electrically conducting when the field-effect transistor power device is in an ON state, any region other than the channel region has an ON resistance exhibiting a positive temperature dependence, and the channel region has an ON resistance exhibiting a negative temperature dependence, and a ratio ΔR on /R on ( −30 ° C.) is 50% or less, where R on ( −30 ° C.) is an ON resistance of the entire power device at −30° C.; and ΔR on is an increase in the ON resistance of the entire power device when a temperature of the power device is varied from −30° C. to 100° C.