NOVELTY - The device has a field effect phototransistor with contact electrodes of a source (S) and a drain (D), respectively. An electric conduction nanostructured unit has a carbon nanotube and is covered with a photosensitive layer absorbing the radiation to be detected. A gate electrode (G) controls spatial distribution of electrical charges generated by the unit and is separated from the unit by a gate dielectric (4). The dielectric has a relative permittivity satisfying a specified condition so that phototransistor`s conductivity after exposition to the radiation is electrically reinitialized.    USE - Used in an imager e.g. color imager, for detecting and storing controlled electromagnetic radiation e.g. radiation in visible region, near ultraviolet radiation, X-rays, and gamma rays, for forming an imaging pixel and for forming a matrix of pixels e.g. pixels for giant telescope (claimed), where the pixel is fabricated on an electronic circuit e.g. pixel addressing circuit.    ADVANTAGE - The device permits to increase filling factor, which is the ratio of sensitive surface of the pixel to its total surface, to reduce the size of the pixel. The carbon nanotube permits to obtain off-state of the phototransistor in a reliable manner, thus maximizing the difference of the conductivity of the phototransistor in response to the radiation. The device forms the pixel in better miniaturization and operating conditions. The permittivity of the dielectric satisfies specified condition, thus permitting electrostatic control of the electric discharge of the nanotube and the layer in an efficient manner, and hence reinitializing the device for forming the pixel in a reliable manner and at any instant irrespective of the received radiation, by applying negative voltage impulse to gate electrode of the imager.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for fabricating a electromagnetic radiation storing and detecting device.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective and transparent schematic view of an electromagnetic detecting and storing device.    Drain (D)    Gate electrode (G)    Source (S)    Electromagnetic radiation detecting and storing device (1)    Gate dielectric (4)