Patent ID: 8289241

Claim:
A personal computer having a display device, said display device comprising: a plurality of source signal lines; a plurality of gate signal lines; a plurality of pixels; a source signal line driving circuit configured to input signals to the plurality of source signal lines wherein the source signal line driving circuit comprises a constant current circuit comprising a first thin film transistor, and a gate signal line driving circuit configured to input signals to the plurality of gate signal lines, wherein each of the plurality of pixels includes an EL element and one switching thin film transistor, said switching thin film transistor comprising: at least two gate electrodes connected with one of said plurality of gate signal lines, each gate electrode comprising a first conductive layer and a second conductive layer, wherein edge portions of the first conductive layer and the second conductive layer are tapered shape; and a semiconductor layer having at least two channel regions, first impurity regions, second impurity regions, and third impurity regions, wherein one of the first impurity regions is connected with one of said plurality of source signal lines, and another one of the first impurity regions is connected with either of a cathode and an anode included in said EL element, wherein the second impurity regions and the third impurity regions are LDD regions, wherein the gate electrode overlaps with the third impurity regions, wherein the gate electrode does not overlap with the second impurity regions, and wherein at least one of the second impurity regions is provided between at least one of the third impurity regions and at least one of the first impurity regions.