In order to examine the electrical and physical properties of Al 2 O 3 layers with dual thickness on a chip, Pt gate/Al 2 O 3 with dual thickness/p-type Si (100) samples were fabricated using atomic-layer deposition, separation photolithography, and 100:1 HF wet etching to remove the first Al 2 O 3 layer. Dual metal-oxide-semiconductor (MOS) capacitors with thin (physical thickness, ϳ4.5 nm, equivalent oxide thicknesses (EOT): 2.8 nm) and thick (physical thickness, ϳ8.2 nm, EOT: 4.3 nm) Al 2 O 3 layers showed a good leakage current density of Ϫ5.4 ϫ 10 Ϫ6 A/cm 2 and Ϫ2.5 ϫ 10 Ϫ9 A/cm 2 at Ϫ1 V, respectively; good reliability characteristics as a result of the good surface roughness; low capacitance versus voltage measurements (C-V) hysteresis; and a good interface state density (ϳ7 ϫ 10 10 cm Ϫ2 eV Ϫ1 near the midgap) as a result of pre-rapid thermal annealing (pre-RTA) after depositing the Al 2 O 3 layer compared with the single MOS capacitors without the pre-RTA. These results suggest that dual Al 2 O 3 layers using the dual gate oxide (DGOX) process can be used for the simultaneous integration of the low power transistors with a thin Al 2 O 3 layer and high reliability regions with a thick Al 2 O 3 layer.