Patent ID: 7588976

Claim:
A method of producing a display device having a substrate on which display unit and a peripheral drive unit are integrally formed, said display unit having pixels arranged in a matrix and pixel transistors switching them ON and OFF integratedly formed, said drive unit having peripheral transistors configuring a drive circuit for scanning the matrix of the pixel transistors integratedly formed, and both of said pixel transistors and peripheral transistors being comprised of thin film transistors obtained by stacking polycrystalline semiconductor thin films and gate electrodes via gate insulating films, including forming a silicon crystalline silicon film or a polycrystalline silicon film over the display unit and the drive unit of said substrate; implanting inactive ions not exerting any influence upon electric characteristics of the active layer into said polycrystalline silicon film so as to convert it once to an amorphous silicon film; and performing recrystallization by heat treating the amorphous silicon film so as to obtain the polycrystalline silicon film again, and forming the film so that a thickness of the polycrystalline silicon constituting the active layer of said pixel transistors becomes thinner than the thickness of the polycrystalline silicon constituting the active layer of said peripheral transistors and thereby an average crystal grain size of the polycrystalline silicon film of said pixel transistors and an average crystal grain size of the polycrystalline silicon film of said peripheral transistors obtained in said recrystallization step differ.