Abstract: A method of fabricating alignment marks on an integrated circuit device including steps of: forming first pad oxide layer and first nitride layer on a P-type semiconductor substrate; coating and patterning first photoresist layer by lithography; partially etching first nitride layer to form first nitride pattern by first photoresist etching mask; and ion implanting N-type ions to form an N-doped region; coating and patterning second photoresist layer by lithography; partially etching first nitride pattern to form second nitride pattern; and ion implanting P-type ions to formed a P-doped region. Next, performing thermally drive in N-type and P-type impurities to form N-well and P-well regions, and growing an oxide layer simultaneously. Finally, the height difference between the oxide layer and the second nitride pattern producing a ladder topography can be used as an alignment mark for the succeeding lithographic processes.