We introduced high-density columnar defects as artificial pinning centers (APCs) for quantized vortices into YBa 2 Cu 3 O 7−x (YBCO) films during the film deposition procedure. APCs were introduced perpendicular to the film surface using nano-sized Y 2 O 3 islands prepared on SrTiO 3 (100) substrates. Varying the deposition parameters and the substrate annealing conditions allowed strong changes in the shape and density of the Y 2 O 3 islands to be induced. Compared to a pure YBCO film, the best performance among the APCs samples was obtained on the Y 2 O 3 -deposited substrate with 5 laser pulses, corresponding to a nominal thickness of 0.2nm. Even when the APC films were prepared using the same deposition conditions, the columnar defects enhanced J c at 77K from 1.8 to 2.7MA/cm 2 (self field) and from 0.06 to 0.10MA/cm 2 (H=5T, H∥c-axis).