The present invention relates to a method for fabrication of a mask capable of stabilizing the size and the thickness thereof.A method for fabrication of a mask according to the present invention comprises a step for successively depositing an oxide layer and a Cr layer on a quartz plate, a step for successively etching said oxide layer and said Cr layer by an E-beam, and a step for extending said oxide in volume by an oxidation process to form a phase-shifter.Therefore, the size and thickness of a mask can easily be controlled by using an oxide instead of PMMA of the photosensitive film as a phase-shifter and endurability of a mask can be improved.