In a semiconductor integrated circuit device including a third gate, the present
invention improves miniaturization and operation speed and reduces a defect density
of an insulator film. In a semiconductor integrated circuit device including a
well of a first conductivity type formed in a semiconductor substrate, a source/drain
diffusion layer of a second conductivity type inside the well, a floating gate
formed over the semiconductor substrate through an insulator film, a control gate
formed and isolated from the floating gate through an insulator film, word lines
formed by connecting the control gates and a third gate formed and isolated from
the semiconductor substrate, the floating gate and the control gate through an
insulator film and different from the floating gate and the control gate, the third
gate is buried into a space of the floating gates existing in a direction vertical
to the word line and a channel.
