A semiconductor device which simplifies the manufacturing process while decreasing the width of separation between a first MOS transistor area and a second MOS transistor area, and a method for manufacturing the semiconductor device. A first MOS transistor and a second MOS transistor configure a bidirectional switch. The first MOS transistor and second MOS transistor each have a vertical trench structure. A first impurity region abuts on the side wall of a first gate trench of a first MOS transistor element outside the first MOS transistor area and is electrically coupled to a first source region.