A semiconductor device, comprising: a first transistor of a second
electric conductivity type formed in a substrate including impurities of
a first electric conductivity type; and a second transistor of the second
electric conductivity type formed in the substrate, a source region of
the second transistor being shared with a source region of the first
transistor; wherein in a lower layer of a gate insulating film of the
first transistor, a first offset layer of the second electric
conductivity type is formed adjacent to a channel region of the first
transistor, in a lower layer of a gate insulating film of the second
transistor, a second offset layer of the second electric conductivity
type is formed adjacent to a channel region of the second transistor, and
in the source region, a first diffusion layer of the first electric
conductivity type and a second diffusion layer of the first electric
conductivity type in the upper layer of the first diffusion layer are
formed, and wherein the second diffusion layer is provided so as to come
in contact with the first and second offset layers via the first
diffusion layer, and the impurity concentration of the first diffusion
layer is higher than the impurity concentration of the substrate.