A method for manufacturing an integrated circuit includes following steps. A substrate including a memory region and a core region is provided. At least two semiconductor word lines, two memory cells in between the two semiconductor word lines, and a semiconductor gate in between the two memory cells are formed in the memory region. A transistor device including a dummy gate is formed in the core region, and a height of the dummy gate is larger than a height of the semiconductor word lines. A protecting layer is formed on the semiconductor word lines, the memory cells, the semiconductor gate and the transistor device. A portion of the protecting layer is removed to expose the dummy gate and followed be removing the dummy gate to form a gate trench in the transistor device. Then a metal gate is formed in the gate trench.