The disclosure provides methods of forming a silicon quantum dots for application in a semiconductor memory device. One example method includes sequentially forming a pad oxide film and a sacrificial insulation film on a silicon substrate; forming a wall layer by selectively etching the sacrificial insulation film; forming a spacer at the side wall of the wall layer; etching the silicon substrate as much as a predetermined thickness using the spacer as a mask, thereby forming a silicon pattern; forming a barrier film for burying the upper surface and the side surface of the silicon pattern; applying isotropic etching to the substrate using the barrier film as a mask; and oxidizing the isotropic etched substrate with thermal treatment.