This invention provides a semiconductor device having high operation performance and high reliability. An LDD region 707 overlapping with a gate wiring is arranged in an n-channel TFT 802 forming a driving circuit, and a TFT structure highly resistant to hot carrier injection is achieved. LDD regions 717, 718, 719 and 720 not overlapping with a gate wiring are arranged in an n-channel TFT 804 forming a pixel unit. As a result, a TFT structure having a small OFF current value is achieved. In this instance, an element belonging to the Group 15 of the Periodic Table exists in a higher concentration in the LDD region 707 than in the LDD regions 717, 718, 719 and 720.

Even when a light shielding film is provided between a transistor and a substrate, a threshold voltage of the transistor can be prevented or suppressed from being shifted. A display device includes light shielding films provided between a substrate and a semiconductor layer of a transistor including a gate electrode and the semiconductor layer. The semiconductor layer includes a source region and a drain region. Both of the light shielding films overlap the semiconductor layer when seen in a plan view, and are spaced apart from each other in a direction.

A thin film transistor includes a substrate, a semiconductor layer, a first insulating layer, and a gate electrode. The gate electrode overlaps the semiconductor layer. The thin film transistor includes a second insulating layer on the gate electrode, and an electrode structure on the second insulating layer. The electrode structure is connected to the gate electrode through a via hole. The thin film transistor includes a source electrode and a drain electrode passing through the first insulating layer and the second insulating layer to be connected to the semiconductor layer. The semiconductor layer includes a channel area overlapping the gate electrode, a source area connected to the source electrode, a drain area connected to the drain electrode, a lightly doped source area, and a lightly doped drain area. The electrode structure overlaps at least one of the lightly doped source area or the lightly doped drain area.

The present invention improves the aperture ratio of a pixel of a reflection-type display device or a reflection type display device without increasing the number of masks and without using a blackmask. A pixel electrode (167) is arranged so as to partially overlap a source wiring (137) for shielding the gap between pixels from light, and a thin film transistor is arranged so as to partially overlap a gate wiring (166) for shielding a channel region of the thin film transistor from light, thereby realizing a high pixel aperture ratio.