Patent ID: 8187935

Claim:
A method of forming an active region structure, comprising: preparing a semiconductor substrate having a cell array region and a peripheral circuit region; forming upper cell mask patterns having a line shape in the cell array region; forming first and second peripheral mask patterns in the peripheral circuit region, the first and second peripheral mask patterns being stacked in sequence and covering the peripheral circuit region, and upper surfaces of the upper cell mask patterns forming a step difference with an upper surface of the second peripheral mask pattern; forming spacers on sidewalls of the upper cell mask patterns to expose lower portions of the upper cell mask patterns and the second peripheral mask pattern; and removing the lower portions of the upper cell mask patterns using the spacers and the first and second peripheral mask patterns as an etch mask, wherein forming the upper cell mask patterns and the first and second peripheral mask patterns includes: sequentially forming an upper mask layer of a stacked material and photoresist patterns on the semiconductor substrate, such that photoresist patterns in the cell array region expose the upper mask layer in the cell array region, and a photoresist pattern in the peripheral circuit region covers the upper mask layer in the peripheral circuit region, etching an upper portion of the upper mask layer using the photoresist patterns as an etch mask, removing the photoresist patterns from the semiconductor substrate, and etching a lower portion of the upper mask layer in the cell array region using the upper portion of the upper mask layer in the cell array region and the upper mask layer in the peripheral circuit region as an etch mask, and wherein the upper mask layer is formed into the upper cell mask patterns in the cell array region and the first and second peripheral mask patterns in the peripheral circuit region, the upper surfaces of the upper cell mask patterns having a lower level than the upper surface of the second peripheral mask pattern due to an etch loading effect of an etching gas after the photoresist patterns are removed.