• A stable laminated Al₂O₃/HfO₂ insulator is developed by atomic layer deposition at a relatively lower temperature of 150 °C.

• The flexible thin-film transistors (TFTs) with bottom-gate top-contacted configuration are fabricated on a flexible substrate with the Al₂O₃/HfO₂ insulator.

• The flexible TFTs present the carrier mobilities of 9.7 cm² V⁻¹ s⁻¹, ON/OFF ratio of ~ 1.3 × 10⁶, subthreshold voltage of 0.1 V, saturated current up to 0.83 mA, and subthreshold swing of 0.256 V dec⁻¹.

Flexible thin-film transistors (TFTs) have attracted wide interest in the development of flexible and wearable displays or sensors. However, the conventional high processing temperatures hinder the preparation of stable and reliable dielectric materials on flexible substrates. Here, we develop a stable laminated Al₂O₃/HfO₂ insulator by atomic layer deposition at a relatively lower temperature of 150 °C. A sputtered amorphous indium-gallium-zinc oxide (IGZO) with the stoichiometry of In_0.37Ga_0.20Zn_0.18O_0.25 is used as the active channel material. The flexible TFTs with bottom-gate top-contacted configuration are further fabricated on a flexible polyimide substrate with the Al₂O₃/HfO₂ nanolaminates. Benefited from the unique structural and compositional configuration in the nanolaminates consisting of amorphous Al₂O₃, crystallized HfO₂, and the aluminate Al–Hf–O phase, the as-prepared TFTs present the carrier mobilities of 9.7 cm² V⁻¹ s⁻¹, ON/OFF ratio of ~ 1.3 × 10⁶, subthreshold voltage of 0.1 V, saturated current up to 0.83 mA, and subthreshold swing of 0.256 V dec⁻¹, signifying a high-performance flexible TFT, which simultaneously able to withstand the bending radius of 40 mm. The TFTs with nanolaminate insulator possess satisfactory humidity stability and hysteresis behavior in a relative humidity of 60–70%, a temperature of 25–30 °C environment. The yield of IGZO-based TFTs with the nanolaminate insulator reaches 95%.