PURPOSE: To obtain the titled device of high resolution by a method wherein a read-out transistor consisting of a main electrode region and a control electrode region provided in a single crystal island region and a photo receiving transistor of the same structure made of amorphous Si are superposed on each other, and the control electrodes thereof are both put in floating state.

CONSTITUTION: An n- type layer 5 is epitaxially grown on all amorphous Si layer 1 having a collector electrode 12 on the back surface and then isolated into island form by means of an SiO2 film 4. Next, a p type base region 6 is formed there, an n+ type emitter region 7 put in floating state being provided therein. The entire surface is covered with an SiO2 film 3, and a wiring 8 contacting the region 7 is adhered by opening a window. Thereafter, an SiO2 film 2 is adhered over the entire surface, apertures being bored in the films 2 and 3, and a p+ type region 401 contacting the region 6 being then buried; thereby constructing the read-out transistor. An n type substrate 403 likewise of island form but single crystal Si which constitutes the photo receiving transistor is made to abut against the upper part thereof via high resistant region 402, where an element region of nearly the same structure is formed.