We demonstrated the high performance back-channel-etched (BCE) amorphous-InGaZnO (a-IGZO) thin-film transistor (TFT) circuits. The TFTs exhibited the field-effect mobility, turn-on voltage and subthreshold swing of 18 cm 2 /V•s, -0.1 V, and 258 mV/dec, respectively. The oscillation frequency of an 11 stages ring-oscillator is ~334.1 kHz, at VDD = 20 V. The 320 stages 11T2C shift-register operated well up to the last stage with rising and falling times of 950 and 690 ns, respectively. Good performance is attributed to damage-free back channel wet etch process and small overlap capacitance between the gate and source/drain electrodes.