Display device and manufacturing method of the same

A manufacturing method of a display device, comprising the steps of:

• forming a gate electrode over a substrate;
• forming a gate insulating film over the gate electrode;
• forming a microcrystalline semiconductor film over the gate insulating film, the microcrystalline semiconductor film including a channel formation region;
• forming a buffer layer over the microcrystalline semiconductor film;
• forming a channel protective layer in a region over the buffer layer, which is overlapped with the channel formation region;
• forming a source and drain regions over the channel protective layer;
• forming a source and drain electrodes over the source and drain regions;
• forming an impurity region by adding an impurity element which imparts one conductivity type selectively in the channel formation region of the microcrystalline semiconductor film, through the buffer layer and the channel protective layer with a use of the source and drain electrodes as masks;
• and
• forming a pixel electrode which is electrically connected to the source and drain electrodes.