Method of manufacturing semiconductor device including pixel electrode containing indium, zinc, and metal element

A method for forming a display device comprising the steps of:

• forming a conductive layer over a substrate;
• forming a first electrode and a second electrode by patterning the conductive layer;
• forming a first insulating layer covering the first electrode and the second electrode;
• forming an oxide semiconductor layer over the first insulating layer;
• forming a first oxide semiconductor layer overlapping with the first electrode and a second oxide semiconductor layer overlapping with the second electrode by patterning the oxide semiconductor layer;
• forming a source electrode and a drain electrode over and in contact with the first oxide semiconductor layer;
• forming an oxide insulating layer over and in contact with the first oxide semiconductor layer, the source electrode, and the drain electrode;
• forming a first opening in the oxide insulating layer, the first opening overlaps with the second oxide semiconductor layer and the second electrode;
• forming a pixel electrode from the second oxide semiconductor layer;
• wherein the step of forming the pixel electrode comprises a step of:
• forming a second insulating layer containing hydrogen over and in contact with the second oxide semiconductor layer in the first opening, and
• forming a liquid crystal layer over the pixel electrode,
• wherein the first oxide semiconductor layer serves as a channel formation region,
• wherein the second electrode, a portion of the first insulating layer, and a portion of the pixel electrode form a capacitor,
• wherein the oxide semiconductor layer contains indium, zinc, and a metal element, and wherein the step of forming the pixel electrode further comprises a step of:
• removing a part of the second insulating layer overlapped with the first opening after the second insulating layer is in contact with the second oxide semiconductor layer.