Display device and electronic device

A display device comprising:

• a transistor over a substrate, the transistor comprising:
• a semiconductor layer;
• and
• source and drain electrode layers over the semiconductor layer;
• and
• an insulating layer over the source and drain electrode layers,
• wherein one of the source and drain electrode layers is a stacked-layer structure of two layers,
• wherein the other of the source and drain electrode layers is a stacked-layer structure of three layers, and
• wherein the insulating layer is in contact with a top surface of the one of the source and drain electrode layers and a top surface of the other of the source and drain electrode layers.

A display device comprising:

• a transistor over a substrate, the transistor comprising:
• a semiconductor layer;
• and
• source and drain electrode layers over the semiconductor layer;
• an insulating layer over the source and drain electrode layers;
• a pixel electrode layer;
• and
• a liquid crystal layer over the pixel electrode layer,
• wherein one of the source and drain electrode layers is a stacked-layer structure of two layers,
• wherein the other of the source and drain electrode layers is a stacked-layer structure of three layers, and
• wherein a pixel electrode layer is over and in contact with the stacked-layer structure of three layers,
• wherein the insulating layer is in contact with a top surface of the one of the source and drain electrode layers and a top surface of the other of the source and drain electrode layers.