| abstract |
An object of the invention is to provide a technique for improving the characteristics of a TFT and realizing an optimum structure of the TFT for the driving conditions of a pixel section and a driving circuit by a small number of photo masks. Therefore, a light emitting device has a semiconductor film, a first electrode and a first insulating film nipped between the semiconductor film and the first electrode. Further, the light emitting device has a second electrode and a second insulating film nipped between the semiconductor film and the second electrode. The first and second electrodes are overlapped with each other through a channel forming area arranged in the semiconductor film. In the case of a TFT in which a reduction in off-electric current is considered important in comparison with an increase in on-electric current, a constant voltage (common voltage) is applied to the first electrode at any time. In the case of a TFT in which the increase in on-electric current is considered important in comparison with the reduction in off-electric current, the same voltage is applied to the first and second electrodes. |