Transparent conducting oxides (TCOs) are well known and have been widely used for a long time in optoelectronics industries. The most popular TCOs have n-type characteristics. However p-type material is not well established and examined. The delafossite-CuAlO2 is one of the p-type TCOs. In this paper, amorphous Cu-Al-O films were deposited onto (100) p-type silicon substrate by magnetron sputtering. After that, the films were annealed at 800°C for 2 h in different partial oxygen levels ranging from 5*10-5 to 1 atm with N2, air, and O2. X-ray diffraction patterns showed that as-deposited films were amorphous. In addition, delafossite-CuAlO2 (R m and P63/mmc phase) appeared at 800°C in N2, but monoclinic-CuO and spinel-CuAl2O4 phases existed in air and O2. The formation of delafossite-CuAlO2 phase can be explained with thermodynamics. The optoelectronic properties of delafossite-CuAlO2 films were also measured. The direct optical bandgap was around at 3.3 eV, which is comparable with literature data. The electrical conductivity was obtained to be 6.8*10-3 S/cm. The hot-probe method employed to measure the electrical property of the films, which indicates that delafossite-CuAlO2 films have p-type characteristics.