Method of forming active region structure

Abstract

A method of forming an active region structure includes 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.