The research on perovskite oxide thin films, interfaces, and super-lattices demands the need for the atomically flat surface of the substrate to realize high-quality epitaxial thin films. In this paper, we report the pH-dependent Buffered NH₄F-HF (BHF) etching and concentration-dependent ACID etching of the SrTiO₃ substrate in different orientations [(001), (110), and (111)]. We have optimized the etching time for both kinds of etching processes. A high-quality step–terrace structure without etch pits is obtained for 2% BHF and 100% ACID solution having a pH value of ~ 3.30. For BHF etching, the optimum etching time depends on the substrate orientation [30 s for STO (001), 40 s for STO (110), and 60 s for STO (111)]. On the other hand, for ACID etching, the optimum etching time is more or less constant for all the orientations. This study might be extended to similar oxides substrates, especially on the exciting KTaO₃.