Embodiments relate to a method of forming an organic light emitting diode (OLED) display device. A first inorganic layer, a first organic layer, and a second inorganic layer are formed on pixel regions of an OLED display device. At least part of a first inorganic layer is formed using atomic layer deposition (ALD), such that the first inorganic layer completely covers particles generated on the OLED. Embodiments also relate to an OLED display device with pixel regions, each pixel region including an OLED, a bank layer across a boundary between adjacent pixel regions, and a first inorganic layer on at least a portion of the OLED and the bank layer. The first inorganic layer includes a first inorganic sub-layer and a second inorganic sub-layer.