An element substrate is provided, including a substrate, a metal layer and a planarization layer. The metal layer is located on the substrate. The metal layer has a first edge in a first direction. The planarization layer is located on the metal layer. The planarization layer includes a contact hole. The contact hole has a contiguous wall and a bottom side. The metal layer is exposed in the bottom side. A contour line of the contiguous wall on a vertical plane is a curved line. The first edge corresponds vertically with a critical point on the contour line. The slope of a tangent line on the critical point of the contour line is smaller than 0.176.