A semiconductor device includes a semiconductor substrate, a first source region and a first drain region each formed from an upper surface of the semiconductor substrate, a first gate electrode formed on the semiconductor substrate between the first source region and the first drain region via a first gate dielectric film, a first trench formed in the upper surface of the semiconductor substrate between the first gate dielectric film and the first drain region in a gate length direction, a second trench formed in the upper surface of the semiconductor substrate between the gate dielectric film and the first drain region in the gate length direction, the second trench being shallower than the first trench, and a first dielectric film embedded in the first trench and the second trench. The first trench and the second trench are in contact with each other in a gate width direction.