METHOD FOR MANUFACTURING TRANSISTOR

摘要

PURPOSE: A method for manufacturing a transistor is provided to prevent a gate electrode from being pitted even if over-etch occurs in an etch process for forming a spacer, by placing an undoped layer in the upper portion of a gate electrode material. CONSTITUTION: A gate oxide layer(102) is formed on a semiconductor substrate(100). The first polysilicon layer(104a) is formed on the gate oxide layer by a predetermined thickness. High density impurity ions are implanted into the resultant structure to dope impurities to the first polysilicon layer. The second polysilicon layer(104b) is formed on the first polysilicon layer. The first and second polysilicon layers in a region except a gate electrode formation part are selectively etched to form a gate electrode composed of the first and second polysilicon layers. The gate oxide layer in a portion not masked by the gate electrode is eliminated. Low density impurity ions are implanted into the resultant structure to form a lightly-doped-drain(LDD) region in the substrate at both edges of the gate electrode. A spacer(110) is formed on both sidewalls of the gate electrode. High density impurity ions are implanted into the resultant structure to dope impurity to the second polysilicon layer constituting the gate electrode. A source/drain region is formed in the substrate at both edges of the spacer.