Abstract: The invention relates a cell device and a cell string for high density flash memory. The cell string includes a plurality of cell devices and switching devices connected to ends of the plurality of cell devices. The cell device includes a semiconductor substrate, an insulating film, a charge storage node composed of nano-sized dots, a control insulating film and a control electrode which are sequentially formed on the semiconductor substrate, without source/drain regions. In the cell string, the silicon substrate enables easy formation of an inversion layer acting as the source/drain regions. The switching device does not include a source or drain region at a side connected to an adjacent cell device but includes a source or drain region at the side opposite to the side connected to the adjacent cell device.