An area sensor of the present invention has a function of displaying an image
in a sensor portion by using light-emitting elements and a reading function using
photoelectric conversion devices. Therefore, an image read in the sensor portion
can be displayed thereon without separately providing an electronic display on
the area sensor. Furthermore, a photoelectric conversion layer of a photodiode
according to the present invention is made of an amorphous silicon film and an
N-type semiconductor layer and a P-type semiconductor layer are made of a polycrystalline
silicon film. The amorphous silicon film is formed to be thicker than the polycrystalline
silicon film. As a result, the photodiode according to the present invention can
receive more light.