METHOD FOR MANUFACTURING ALIGNMENT KEY OF SEMICONDUCTOR DEVICE

PURPOSE: A method for manufacturing an alignment key of a semiconductor device is provided to easily control an overlay by changing a lattice pattern of the alignment key to a silicon-oxidation layer pattern to generate a difference of a reflection rate in an alignment key lattice when the alignment key is formed by using a shallow trench isolation(STI) process. CONSTITUTION: A pad oxidation layer and a nitride layer are formed on a scribe line of a semiconductor substrate(10), the scribe line separating dies on which a cell pattern is formed. The nitride layer and pad oxidation layer are etched to expose a non-active region of the substrate, and the exposed region is etched to form a trench. An oxidation layer is formed on the entire surface of the substrate to fill up the trench. The entire surface is firstly etched until the nitride layer are exposed. The nitride layer is eliminated. The oxidation layer is secondly etched to form a field oxidation layer(24A). The substrate on both sides of the field oxidation layer is etched a predetermined depth to form an alignment key having a step difference.