Display device and manufacturing method thereof

A display device comprising:

• a first substrate;
• a photo transistor which is disposed on the first substrate and operated by light;
• and
• a switching transistor connected to the photo transistor,
• wherein
• the photo transistor comprises:
• a light blocking film on the first substrate,
• a first gate electrode on the light blocking film and contacting the light blocking film,
• a first semiconductor layer comprising crystalline silicon germanium, on the first gate electrode and overlapping the light blocking film, the crystalline silicon germanium first semiconductor layer defining a channel of the photo transistor, and
• a first source electrode and a first drain electrode on the crystalline silicon germanium first semiconductor layer,
• the switching transistor comprises:
• a second gate electrode on the first substrate,
• a second semiconductor layer comprising crystalline silicon germanium, on the second gate electrode and overlapping the second gate electrode, the crystalline silicon germanium second semiconductor layer defining a channel of the switching transistor, and
• a second source electrode and a second drain electrode on the crystalline silicon germanium second semiconductor layer, and
• the crystalline silicon germanium first semiconductor layer of the channel of the photo transistor is disposed between the first substrate, and each of the first source electrode and first drain electrode, respectively, and the crystalline silicon germanium second semiconductor layer of the channel of the switching transistor is disposed between the first substrate, and each of the second source electrode and second drain electrode, respectively.