A display device includes a first substrate, a gate line disposed on the first substrate and including a gate electrode, a gate insulating layer disposed on the gate line, a semiconductor layer disposed on the gate insulating layer, a data line disposed on the semiconductor layer and connected to a source electrode, a drain electrode disposed on the semiconductor layer and facing the source electrode and a passivation layer disposed on the data line, in which the semiconductor layer is formed of an oxide semiconductor including indium, tin, and zinc. The indium is present in an amount of about 5 atomic percent (at %) to about 50 at %, and a ratio of the zinc to the tin is about 1.38 to about 3.88.