Patent ID: 7394098

Claim:
A display device having pixel drive transistors and peripheral circuit transistors for controlling operations of said pixel drive transistors, wherein: said peripheral circuit transistor comprises an insulating substrate, a first insulating buffer layer formed on a surface of said insulating substrate, a first silicon layer formed on a surface of said first insulating buffer layer; a second insulating buffer layer formed on a surface of said first silicon layer and a second silicon layer formed on a surface of said second insulating buffer layer, said second silicon layer being an active layer of said peripheral circuit transistor; and said pixel drive transistor comprises a third silicon layer formed on the surface of said first insulating buffer layer, said third silicon layer being a same layer as said first silicon layer and an active layer of said pixel drive transistor, and wherein said third silicon layer is made of polycrystalline grains whose average crystal grain diameter is smaller than an average crystal grain diameter of said second silicon layer.