A phase shift mask (24) used for manufacturing semiconductor devices includes a pattern layer (26) that contains the predetermined pattern of a desired semiconductor feature which is formed in a plurality of apertures in the pattern layer (26). A conformal coating (27) is applied to the mask (24) to create a phase shift region (31, 36, 37) within a predetermined distance (29) of each aperture in the pattern layer (26). The conformal coating (27) forms two regions (31, 36, 37) (32) having different thicknesses. The phase of light passing through the thicker or phase shift region (31, 36, 37) is shifted relative to light passing through the thin region (32).