In this letter, we use a dual-gate (DG) structure together with nanometer dotlike doping (NDD) in active channel to produce a-IGZO thin-film transistors with very high current drive. With DG operation, the output current increases from 0.14 mA of the conventional device to 0.76 mA of the NDD device. The enhanced lateral field and improved carrier accumulation in DG operation may explain the significantly enlarged drive current. Particularly, simulated electron distribution reveals that high carrier concentration is induced under NDD regions in DG operation. The device without NDD, however, does not exhibit improved drive current in DG operation.