The active layer of an n-channel TFT is formed with a channel forming region, a first impurity region, a second impurity region and a third impurity region. A substrate comprises circuitry and electrodes for electrostatically deflecting micromirror elements that are disposed within an array of such elements forming the spatial light modulator. It is also possible to vary the modulation rate by varying the clock frequency of a driving signal to be input to the optical modulator.