Patent ID: 7407840

Claim:
A method of production of a display device having a substrate on which a 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, said drive unit having peripheral transistors comprising a drive circuit for scanning the matrix of pixel transistors, 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, said method including: a film forming step of forming a polycrystalline silicon film over a display unit portion and a drive unit portion of said substrate, portions of the polycrystalline silicon film constituting an active layer for the pixel transistors and the peripheral transistors; an impurity implantation step of implanting electrically inactive impurities that do not exert any influence upon electrical characteristics of the active layer into said polycrystalline silicon film so as to convert the polycrystalline silicon film to an amorphous silicon film; and a recrystallization step of heat treating the amorphous silicon film so as to obtain the polycrystalline silicon film again, wherein said impurity implantation step is carried out so that the impurity implantation amount differs between portions of said polycrystalline silicon film portion corresponding to said display unit and portions of said polycrystalline silicon film portion corresponding to said drive unit, 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 differ.