Display device

A display device, comprising:

• a substrate;
• a polycrystalline silicon film on the substrate, the polycrystalline silicon film including a first surface facing the substrate and a second surface opposite to the first surface;
• a first buffer film between the substrate and the polycrystalline silicon film;
• a second buffer film between the substrate and the polycrystalline silicon film, the second buffer film including one surface contacting the first surface of the polycrystalline silicon film and another surface opposite to the one surface;
• and
• a gate insulating layer disposed on the polycrystalline silicon film, the gate insulating layer contacting the second surface of the polycrystalline silicon film,
• wherein a thickness of the second buffer film is different from a thickness of the first buffer film,
• wherein the second surface of the polycrystalline silicon film has a third root mean square (RMS) roughness range,
• wherein the third RMS roughness range is more than 1.5 nm,
• wherein the polycrystalline silicon film includes hydrogen ions, and an average concentration of the hydrogen ions in a vicinity of the first surface of the polycrystalline silicon film is greater than an average concentration of the hydrogen ions in a vicinity of a center of the polycrystalline silicon film,
• wherein the vicinity of the center of the polycrystalline silicon film is defined as a first region which is a section of the polycrystalline silicon film extending from a center point of the polycrystalline silicon film toward the first surface of the polycrystalline silicon film by a depth of 50 Å, and extending from the center point of the polycrystalline silicon film toward the second surface of the polycrystalline silicon film by a depth of 50 Å, and
• wherein the vicinity of the first surface of the polycrystalline silicon film is defined as a second region which is a section of the polycrystalline silicon film extending from the first surface of the polycrystalline silicon film toward the second surface of the polycrystalline silicon film by a depth of 100 Å.