Circuit substrate, manufacturing method thereof and display device

The purpose of the present invention is to provide a circuit substrate which has reduced Cgd capacitance, sufficiently prevents the Cgd capacitance from affecting applied voltage, and can obtain sufficient circuit substrate reliability; and to provide a manufacturing method of said circuit substrate, and a display device. The present circuit substrate comprises a semiconductor element arranged on a transparent substrate, wherein the semiconductor element is provided with an oxide semiconductor layer, and the circuit substrate is provided with an etching stopper layer and a conductor layer. When the main surface of the substrate is viewed planarly, there is a region which overlaps with neither the etching stopper layer nor the conductor layer, and at least one part of said region overlaps with a cutout portion of the oxide semiconductor layer. When the main surface of the substrate is viewed planarly, a part of the edge of the cutout portion of the oxide semiconductor is located beyond the edge of the etching stopper layer in the etching stopper layer direction.