Highly (002)-oriented Al-doped zinc oxide (AZO) thin films with the thickness of less than 200 nm have been deposited on an oxygen-controlled homo-seed layer at 200 °C by DC magnetron sputtering. With the homo-seed layer being employed, the full-width at half maximum (FWHM) of the (002) diffraction peak for the AZO ultra-thin films decreased from 0.33° to 0.22°, and, the corresponding average grain size increased from 26.8 nm to 43.0 nm. The XRD rocking curves revealed that the AZO ultra-thin film grown on the seed layer deposited in atmosphere of O₂/Ar of 0.09 exhibited the most excellent structural order. The AZO ultra-thin film with homo-seed layer reached a resistivity of 4.2 × 10^–4 Ω cm, carrier concentration of 5.2 × 10²⁰ cm^–3 and mobility of 28.8 cm² V^–1 s^–1. The average transmittance of the AZO ultra-thin film with homo-seed layer reached 85.4% in the range of 380–780 nm including the substrate.