Thereafter, the first initial word line structure part is etched to form avoidance region BR in the first initial word line structure part, so as to form the first word line structure part 200A. Illustratively, the first initial word line structure part may be etched by using a photoetching process and an etching process, so that the avoidance region BR is formed in the first initial word line structure part to form the first word line structure part 200A. For example, with reference to FIG. 3I, the photoetching process is adopted to form an avoidance mask BRM, which exposes the portions of the first initial word line structure part in which the avoidance region BR are to be formed. Then, with reference to FIG. 3J, the avoidance mask BRM is used as an etching mask, a vapor phase etching process is adopted, and etching gas may be one or more of SF6, CF4, Cl2, CHF3, O2 or Ar, so as to achieve a certain etching selection ratio. The exposed W layer in the first initial word line structure parts are subjected to vapor phase etching, so as to form concave regions AC0 in the W layers of the first initial word line structure parts to serve as avoidance regions BR.