| 摘要 |
A method for fabricating a mask ROM is provided to guarantee CD uniformity in a photolithography process for forming a code mask by performing a code process after a planarization process for forming a tungsten plug is finished. On a substrate(1) including a plurality of cell gates(21) and a logic gate(31), an interlayer dielectric(4) is formed which has a tungsten plug(5) connected to a part of the logic gate. The interlayer dielectric is selectively etched to form a plurality of code holes(C) exposing the upper part of the cell gate. A code mask(51) exposing a part of the cell gate into which code ions are to be implanted is formed on the interlayer dielectric having the code holes. A code ion implantation process is performed to form a code region(3) in the substrate under the cell gate exposed by the code mask. The process for forming the code hole includes the following steps. A pre-align code mask is formed on the interlayer dielectric, exposing a portion corresponding to the cell gate. The interlayer dielectric exposed by the pre-align code mask is etched. The pre-align code mask is removed.
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