An organic light emitting device is disclosed. In one embodiment, the organic light emitting device includes red (R), green (G) and blue (B) lower electrodes formed on a substrate. R, G, B organic thin film layers are formed on the R, G, B lower electrodes, respectively. Additionally, an upper single or multilayer electrode is formed over the substrate. Portions of the upper electrode that correspond to the R, G, B organic thin film layers, respectively, are formed to each have a different thickness. Various methods for forming the upper electrode using a fine metal mask, a halftone mask, and single and multiple photolithography processes are also disclosed.