Liquid crystal display device and manufacturing method of liquid crystal display device

A manufacturing method of an LCD device including gate lines and source lines which are provided in a grid pattern, pixel electrodes arranged in a matrix pattern so as to correspond to intersections of the gate lines and the source lines, an auxiliary capacitor electrode that forms auxiliary capacitance between the auxiliary capacitor electrode itself and the pixel electrode, and switching elements configured to apply an image signal voltage supplied from the source line to the pixel electrode according to a scanning signal applied from the gate line, the switching element being comprised of oxide semiconductor, and the auxiliary capacitor electrode being provided between the source line and the pixel electrode and comprised of oxide semiconductor having lowered resistance, comprising the steps of:

• forming a conductor layer on a substrate and patterning the conductor layer into the source lines;
• forming an oxide semiconductor layer over the source line and patterning the oxide semiconductor layer into regions serving as a source electrode, a drain electrode, and a channel region of the switching element and a region serving as the auxiliary capacitor electrode;
• sequentially forming an insulating film layer and a conductor layer on the oxide semiconductor layer and patterning the insulating film layer and the conductor layer into a gate insulating film, the gate line, and a gate electrode;
• lowering resistance of the oxide semiconductor layer by using the gate electrode as a mask to form the source electrode and the drain electrode of the switching element and the auxiliary capacitor electrode;
• and
• forming a conductor layer over the drain electrode of the switching element and the auxiliary capacitor electrode and patterning the conductor layer into the pixel electrode.