Semiconductor device and fabrication method thereof

A fabrication method of a semiconductor device, comprising:

• providing a to-be-etched material layer;
• forming a plurality of discrete sacrificial layers on the to-be-etched material layer;
• forming first initial spacers on sidewalls of each of the discrete sacrificial layers in an extension direction of each of the discrete sacrificial layers, wherein each first initial spacer includes a first bottom region and a first top region on the first bottom region;
• forming third initial spacers on sidewalls of each of the discrete sacrificial layers in a direction perpendicular to the extension direction of each of the discrete sacrificial layers when forming the first initial spacers, wherein the third initial spacers and the adjacent first initial spacers together form ring structures and each third initial spacer includes a third bottom region and a third top region on the third bottom region;
• removing the sacrificial layers;
• removing the first top region of each first initial spacer to form a first spacer from each first bottom region and removing the third top region of each third initial spacer to form a third spacer from each third bottom region;
• removing the third spacer and a portion of the first spacer by a first directed ribbon-beam plasma etching process;
• forming second spacers on sidewalls of each first spacer after removing the third spacer;
• removing the first spacers;
• and
• etching the to-be-etched material layer by using the second spacers as a mask.