Patent ID: 8420453

Claim:
A method of forming an active region structure, comprising: preparing a semiconductor substrate including a cell array region and a peripheral circuit region; forming preliminary cell active regions in the cell array region of the semiconductor substrate; and forming cell active regions in the preliminary cell active regions and at least one peripheral active region in the peripheral circuit region of the semiconductor substrate, such that the preliminary cell active regions, the active regions, and the at least one peripheral active region are integrally formed with the semiconductor substrate and protrude from the semiconductor substrate, wherein forming the preliminary cell active regions includes: forming a pad layer to cover an entire surface of the semiconductor substrate; forming first buffer patterns and a buffer layer on the pad layer in the cell array region and the peripheral circuit region of the semiconductor substrate, respectively; forming sacrificial patterns between the first buffer patterns; forming second buffer patterns in the sacrificial patterns, respectively, the first and second buffer patterns having a line shape and corresponding to the preliminary cell active regions; and forming first cell trenches in the cell array region of the semiconductor substrate to correspond to the sacrificial patterns.