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To reduce the secondary emission yield of an RF window ceramic so as to suppress the occurrence of a multipactor, we propose coating the window with a titanium nitride (TiN) film by atomic layer deposition. We investigate two groups of samples with film thicknesses of 56 and 8 nm, respectively, to analyze the composition and optimize the coating thickness of the TiN film on the ceramic. For the first group of samples (56 nm films), x-ray photoelectron spectroscopy (XPS) results show that the film can be divided into three mixed layers: a top layer composed of TiOxNy and TiO2; a middle layer consisting of TiN, TiOxNy, TiO2, and TiC; and a bottom layer called a diffusion layer, formed by decreasing TiN, TiOxNy, TiO2, TiC, and increasing A l 2 O 3 as the ceramic is approached. The depth of this bottom layer is ∼8 nm. Two more films (8 nm films) in the second group of samples were grown on a 96 ceramic and silicon to determine the sheet resistance, those on silicon is ∼1 kΩ/□ as measured by spectroscopic ellipsometry. According to the XPS results of the two 8 nm films, the content of TiOxNy and TiO2 increased while TiN content decreased in the film on 96 ceramic, compared to the film on silicon. Therefore, the 8 nm film is suitable for use as a coating for the RF window to weaken the multipactor effect and lower conductivity. To test the film performance, an RF ceramic window is coated with an 8 nm TiN film. Low-power measurements show that, within a frequency of 100 MHz, the 8 nm film on the RF ceramic window has a negligible effect on its transmission characteristics. 8 kW RF power tests indicate that the film coating can significantly improve the power transmission, anti-multipaction, and stability of the RF window.