A capacitor may have a pre-treatment layer formed on a lower electrode, reaction to a dielectric layer and/or deterioration of capacitor characteristics may be suppressed. At least part of the dielectric layer may be oxidized or nitridized after being oxidized, and increases in leakage current may be suppressed. In a method of fabricating a capacitor, a plasma treatment performed before and after the forming of the dielectric layer within the batch-type equipment may cause retention time between the plasma treatment and the deposition of the dielectric layer to be the same or substantially the same for each wafer and/or capacitors may show smaller variations in layer characteristics between wafers.