The semiconductor device includes a plurality of transistors, wherein one of
the transistors that has the thinnest gate dielectric layer is selected to serve
as a power source protection element, among a plurality of transistors, each having
a gate dielectric layer of an independently set film thickness, disposed on a same
substrate to be operated by a voltage from a same power source. Also, a threshold
voltage of the transistor selected as the power source protection element is set
higher than other transistor that also has the thinnest gate dielectric layer.
