Method for forming extension by using double etch spacer

摘要

A method for forming extension by using double etch spacer. The method includes at least the following steps. First a semiconductor substrate is provided. Then, the gate is formed on the substrate. A first spacer is formed on a sidewall of the gate. Then, numerous first ions are implanted in the substrate by a mask of both the gate and the first spacer to form the source/drain region. Then, the second spacer is formed by etching the first spacer, wherein the width of the second spacer is less than the width of the first spacer. Finally, numerous second ions are implanted in the substrate by a mask of both the gate and the second spacer to form an extension.