A first transistor includes a first impurity layer of a first conduction type formed in a first region of a semiconductor substrate, a first epitaxial semiconductor layer formed above the first impurity layer, a first gate insulating film formed above the first epitaxial semiconductor layer, a first gate electrode formed above the first gate insulating film, and first source/drain regions of a second conduction type formed in the first epitaxial semiconductor layer and in the semiconductor substrate in the first region. A second transistor includes a second impurity layer of the first conduction type formed in a second region of the semiconductor substrate, a second epitaxial semiconductor layer formed above the second impurity layer and being thinner than the first epitaxial semiconductor layer, a second gate insulating film formed above the second epitaxial semiconductor layer, a second gate electrode formed above the second gate insulating film, and second source/drain regions of the second conduction type formed in the second epitaxial semiconductor layer and in the semiconductor substrate in the second region.