| 摘要 |
Formation of an isolation region and an alignment mark different in depth in a semiconductor device is disclosed. Phenol resin positive resist has the property that when selective exposure process is implemented to such a resist to apply heat treatment thereto in an amine gas atmosphere such as ammonium, there results the state where only a photosensitive agent at the portion in which light reaction takes place is escaped or gotten away, so this resin portion is insoluble in an alkali developer. By making use of this property, when exposure process is implemented only to the region portions to be etched different in depth to carry out baking, only the position is established by a single mask. Thereafter, only the alignment mark portion required to be deeper of the regions to be etched is etched exposed to light to etch it thereafter to allow only the isolation region to be exposed to light to etch it. Thus, the alignment mark portion becomes deeper than the isolation region by two etching process steps.
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