An etchant composition, and methods of patterning a conductive layer and
manufacturing a flat panel display device using the same are provided.
The etchant composition may include phosphoric acid, nitric acid, acetic
acid, water and an additive, wherein the additive includes a
chlorine-based compound, a nitrate-based compound, and an oxidation
regulator. In addition, the flat panel display device may be manufactured
by patterning a gate electrode, source/drain electrodes and a pixel
electrode using the same etchant composition. The gate electrode,
source/drain electrodes and the pixel electrode may be formed of
different conductive materials. Accordingly, processes are simplified so
that manufacturing costs may be reduced and productivity may be improved.