The invention makes it possible to form thyristers and SCRs that show a good
discharge efficiency upon application of static electricity in semiconductor devices
using a SOI substrate. A semiconductor device is equipped with a connection terminal
for connection with an external element, a dielectric substrate having a semiconductor
layer formed therein, a first region of a first conductive type that is formed
in the semiconductor layer and electrically connected to the connection terminal,
a second region of a second conductive type that is formed in the semiconductor
layer and electrically connected to the first region, a third region of the first
conductive type that is formed adjacent to the second region in the semiconductor
layer, and a fourth region of the second conductive type that is formed adjacent
to the third region in the semiconductor layer.
