PURPOSE: To improve accuracy by subjecting an n type silicon semiconductor layer having high doner concn. to etching treatment on an n type silicon wafer having a low doner concn. thereby forming a capillary column groove on the silicon substrate.

CONSTITUTION: The n type silicon semiconductor layer having a prescribed size and shape and a high doner concn. on the specular surface of the silicon wafer 1 is formed. The wafer 1 is then put into an electrolytic cell 13 having a heater 12 and is subjected to the etching treatment by using an anisotropic etching agent such as potassium hydroxide with the n type silicon semiconductor layer having the high doner concn. of said wafer as an anode via a connector 16 and a platinum plate 14 as a cathode. The n type silicon semiconductor layer having the prescribed shape and high doner concn. is allowed to remain on the wafer 1 by the difference in the etching speed between the wafer 1 and the layer 9 by which the substrate for the column is obtd.