Abstract
The fabricating method of a thick gate dielectric layer transistor is disclosed. A substrate including a first and a second regions and isolation structures is provided. A pad layer and a masking layer are formed on the substrate between the isolation structures. After the masking layer and the pad layer in the second region are removed, a dielectric layer and a conductive layer are sequentially formed on the substrate. The conductive layer, the dielectric layer and the pad layer are patterned to form a first gate structure in the first region and a second gate structure in the second region. A first source region and a first drain region are respectively formed in the substrate adjacent to the first gate structure, and a second source region and a second drain region are formed respectively in the substrate adjacent to the second gate structure.