Methods of forming dual gate of semiconductor device

A method for forming a dual gate of a semiconductor device, the method comprising the steps of:

• forming a first polysilicon layer doped with p-type impurity ions and a second polysilicon layer doped with n-type impurity ions on a first region and a second region of a semiconductor substrate, respectively;
• and
• first wet cleaning the first and second polysilicon layers by using deionized water containing O3;
• second wet cleaning the first and second polysilicon layers by using a buffered oxide etchant (BOE) as a cleaning solution;
• third wet cleaning the first and second polysilicon layers by using deionized water containing O3;
• and
• dry cleaning the first and second polysilicon layers,
• wherein the first set cleaning, the second wet cleaning, the third wet cleaning, and the dry cleaning are performed sequentially.