Abstract: A charge storage tube includes a target comprising a semiconductor substrate, an insulating layer formed on the semiconductor substrate and a metal electrode formed on the insulating layer, wherein a target potential of the target can be changed so that it becomes not only below a first cross-over potential but also over the first cross-over potential. In the charge storage tube, a signal is written in the target by a signal writing means to generate pairs of electron-hole in the target, a surface potential of the insulating layer with the written signal is changed so as to become over the first cross-over potential, and the written signal is read out by scanning electron beams on the target.