The method of forming the transistor and recess gate thin film transistor, with a low impurity concentration drain of self-aligned

摘要

PROBLEM TO BE SOLVED: To provide a recessed-gate thin film transistor (RG-TFT) with a self-aligned lightly doped drain (LDD), and a corresponding forming method.;SOLUTION: A method related to the present invention comprises: a step of depositing an insulator covering a substrate; a step of etching a trench, which has a bottom and sidewalls, in the insulator; a step of forming an active silicon (Si) layer covering the insulator and the trench, and of forming a gate oxide layer covering the active Si layer; and a step of forming a recessed gate electrode in the trench. The TFT is doped, and LDD regions covering the trench sidewalls are formed in the active Si layer. Each LDD region has a length that extends from the top of the trench sidewall to the trench bottom, and a doping concentration of the LDD region which decreases according to the LDD length. In other words, the LDD length is directly related to the depth of the trench.;COPYRIGHT: (C)2008,JPO&INPIT