In one embodiment, a semiconductor device includes first and second semiconductor layers of a first conductivity type above a substrate via a first film, a first electrode above the second semiconductor layer, and a second electrode disposed on a side of the first electrode or an opposite side of the first electrode with respect to the second semiconductor layer. An air conditioner includes a compressor, an outdoor heat exchanger, an indoor heat exchanger, an electronic component box and an electronic component box heat exchanger. The outer sleeve is spaced apart from the inner core.