Method for forming a MOS transistor having lightly dopped drain regions and structure thereof

摘要

A MOS transistor having a LDD structure is described. In accordance with the present invention a MOS transistor includes a low impurity concentration region formed in a semiconductor film between an end of a gate electrode and a source or drain. The transistor includes an insulating film extending beyond the gate electrode in the direction of the source and drain, the insulating film having a thicker portion over the channel region of the semiconductor film and a thinner portion over the source and drain regions of the semiconductor film, such that LDD regions can be formed by utilizing the thickness difference between the thick portion of the insulating film and the thin portion of the insulating.