We propose a new kind of planar waveguide Bragg grating structure, i.e., planar waveguide moiré grating (MG), which is formed by two transverse adjacent gratings with slightly different Bragg wavelengths. It is found that this kind of structure shows the same light properties as the conventional MG that is realized by superimposing two Bragg gratings. Because the proposed MG structure is a planar pattern, the fabrication becomes much easier if applying a semiconductor microfabrication process, which is very beneficial for its applications in photonic integrated devices. Similar to the well-known Vernier effect, the coupling coefficient distribution can be easily adjusted by the alignment of the two adjacent gratings. Consequently, some special grating profiles can be achieved, such as perfect apodization with two sides of the coupling coefficient approaching zero. One important potential application of these specific features is the distributed feedback (DFB) semiconductor laser for improved properties, such as reduced spatial-hole burning and more power extraction. Some design examples are also given in this paper.