A semiconductor device includes a transistor region, a first guard ring, a second guard ring, and a silicide region. A first-conductive-type transistor is formed in the transistor region. The first guard ring is a second-conductive-type first impurity diffusion layer surrounding the transistor region with a first width, and is coupled to a first reference potential. The second guard ring is a first-conductive-type transistor second impurity diffusion layer surrounding the first guard ring with a second width. The silicide region is formed on the surface of the second guard ring such that substantially no silicide is formed on a portion of the surface of the second guard ring on the side facing a drain region of the first-conductive-type transistor, and is connected to a second reference potential line whose potential is higher than that of the first reference potential line.