A method for fabricating zero order nulled silica grating phase masks for 248 nm KrF excimer laser is described. Perfect silica mask gratings with the period of 1.085 μm have been produced using bilayer resist and proper techniques for pattern transfer. Exprimental measurements show that the zero order diffraction efficience is less than 6%. Etch of silica substrates is performed by reactive ion etching in CHF 3/O 2. Theoretical analysis shows that these phase masks can be used for producing grating pattern by self-interference and for fabricating UV written fiber Bragg gratings.