A semiconductor device can easily reduce a leak current which flows when a reversely-staggered-type TFT element in which an active layer is made of polycrystalline semiconductor is turned off. The semiconductor device includes a reversely-staggered-type TFT element in which a semiconductor layer, a source electrode and a drain electrode are arranged on a surface of an insulation film, and a portion of the source electrode and a portion of the drain electrode respectively get over the semiconductor layer. The active layer of the semiconductor layer is mainly made of polycrystalline semiconductor constituted of strip-shaped crystals elongated in the channel length direction of the TFT element, and is configured in a plan view such that the source electrode and the drain electrode are respectively pulled out from positions above the active layer in the channel width direction of the TFT element and in the directions opposite to each other, and the source electrode intersects with only one side out of two sides of the active layer which extend in the channel length direction, and the drain electrode intersects with only another side out of two sides of the active layer which extend in the channel length direction.