Method of manufacturing a semiconductor device

A method of manufacturing a semiconductor device, comprising:

• forming a gate electrode on a semiconductor substrate;
• forming an oxide and nitride layers as a first sidewall layer on both sides of the gate electrode by CVD to cover the gate electrode;
• depositing an undoped layer composed of any one of SiO2, Si3N4, and SiON on the semiconductor substrate to cover the oxide layer and the gate electrode;
• forming a doped layer by ion-implanting impurities using the undoped layer as a target;
• selectively etching the oxide and doped layers in such a way that the first sidewall and doped layers are left only on both sides of the gate electrode;
• forming an LDD region on the semiconductor substrate by out-diffusing the impurities contained in the doped layer;
• removing the doped layer;
• forming a spacer on both sides of the first sidewall layer;
• and
• forming a source/drain region on other part of the active region by implanting the impurities thereto using the spacer as an ion implantation mask.