Patent ID: 7525523

Claim:
A semiconductor device comprising: a plurality of pixels, each of the pixels having a light receiving portion and a display portion; a reset gate signal line; a sensor gate signal line; a sensor output wiring connected to an electric current power supply; a sensor electric power source line for maintaining a constant electric potential; a first driver circuit selecting the light receiving portion of a pixel; a second driver circuit to which is input a signal about a light receiving state of the light receiving portion selected by the first driver circuit; a third driver circuit selecting the display portion of a pixel; and a fourth driver circuit outputting a signal for display to the display portion selected by the third driver circuit, wherein the light receiving portion comprises a reset TFT, a buffer TFT, a selection TFT and a photodiode, wherein semiconductor layers of the reset TFT, the buffer TFT, the selection TFT and the photodiode are formed on a same insulating film, wherein a source region of the reset TFT is connected to the sensor electric power source line, wherein a drain region of the reset TFT is connected to a gate electrode of the buffer TFT and to the photodiode, wherein a drain region of the buffer TFT is connected to the sensor electric power source line; wherein one of a source region and a drain region of the selection TFT is connected to the sensor output wiring, and the other is connected to a source region of the buffer TFT; wherein a gate electrode of the selection TFT is connected to the sensor gate signal line; and wherein the plurality of pixels, the first driver circuit, the second driver circuit, the third driver circuit and the fourth driver circuit are formed over a same substrate.