PURPOSE: To form a sufficiently small opening pattern by forming an upper resist layer, consisting of a material having a low reactive ion etching speed and including no silicon, on a flattened layer, and after sequential patterning, performing reactive ion etching.

CONSTITUTION: A flattened layer 24 is patterned by using an upper layer pattern 25a as a mask to form a lower layer pattern 24a. This patterning is carried out by over etching by means of reactive ion etching. Then, by using both of the formed lower layer pattern 24a and the upper pattern layer pattern 25a remaining thereon as a mask, a buffer layer 23 and a light shielding layer 22 are etched by means of reactive ion etching. Thereupon, a mask with a high aspect ratio is obtained as a result of combining the lower layer pattern 24a and the upper pattern layer pattern 25a, so that a high precision small opening pattern can be formed.