Abstract: In this paper,a novel fabrication technique to obtain silicon crystalline flat planes is described.The selected Si crystalline planes that are not always the planes having the lowest etching rate are pre-obtained by deep-RIE.Si anisotropic wet etching generates the flat crystalline planes with EPW after the deep-RIE.The proposed technique is demonstrated by fabricating a solid polymer dye micro-cavity laser that is molded by the etched Si cavity.The lasing spectra confirm that the planes are optically smooth by measuring the sidewalls of the Si mold.