The present disclosure relates to a semiconductor device, an array substrate, and a method for fabricating the semiconductor device. The semiconductor device comprises a substrate, a thin film transistor formed on the substrate, and a first light detection structure adjacent to the thin film transistor, wherein the first light detection structure includes a first bottom electrode, a top electrode, and a first photo-sensing portion disposed between the first bottom electrode and the first top electrode, one of a source electrode and a drain electrode of the thin film transistor is disposed in the same layer as the first bottom electrode of the first light detection structure; the other of the source electrode and the drain electrode of the thin film transistor is used as the first top electrode.