Active matrix substrate and method for manufacturing the same

A method for manufacturing an active matrix substrate, comprising:

• a step of forming a plurality of gate lines and gate electrodes of a plurality of switching elements in a first wiring layer;
• a step of forming a gate insulating film, forming a first semiconductor film in a first semiconductor layer, and forming a second semiconductor film in a second semiconductor layer;
• a source layer formation step of forming, in a second wiring layer, a first conductor part to be a base of a main conductor part of a plurality of data lines, and a second conductor part to be a base of a source electrode and a drain electrode of the switching element, while patterning the first and second semiconductor films to form a second semiconductor part to be a base of a first semiconductor part located under the main conductor part, a channel region of the switching element which is located in the first semiconductor layer, and a third semiconductor part to be a base of a semiconductor part located under the source electrode and the drain electrode in the second semiconductor layer;
• a pixel electrode layer formation step of forming, in a pixel electrode layer, a pixel electrode, a third conductor part located on the main conductor part, and a conductor part located on the source electrode and the drain electrode, while patterning the first and second conductor parts, a portion of the second semiconductor part which is formed in the second semiconductor layer, and the third semiconductor part, to form the main conductor part, the source electrode, the drain electrode, the first semiconductor part, and the semiconductor part;
• a step of forming a protective insulating film in a layer over the pixel electrode, and
• a step of forming a common electrode in a layer over the protective insulating film, wherein
• in the pixel electrode layer formation step, a portion of the first semiconductor part which is formed in the second semiconductor layer is formed larger than the main conductor part and the third conductor part, and the semiconductor part is formed larger than the source electrode, the drain electrode, and the conductor part.