There is provided a semiconductor device that improves reliability. The impurity concentrations of a p++ source region and a p++ drain region are 5×1020 cm−3 or more. The channel-region-side end portion of a first insulating film is disposed on a p+ source region. The end portion has an inclined surface where the first insulating film thickness is reduced from the p+ source region toward a channel region. The channel-region-side end portion of a second insulating film is disposed on a p+ drain region. The end portion has an inclined surface where the second insulating film thickness is reduced from the p+ drain region toward the channel region. A gate electrode is disposed on the channel region, the p+ source region, the p+ drain region, and the inclined surfaces of the first and the second insulating films through a gate insulating film including an aluminum oxide film.