A method of fabricating a semiconductor device includes the steps of: providing a semiconductor structure including a memory region and a logic region. The semiconductor structure includes a first interlayer dielectric and at least one magnetoresistive random access memory (MRAM) cell disposed on the first interlayer dielectric, and the MRAM cell is disposed in the memory region; depositing a second interlayer dielectric covering the first interlayer dielectric and the at least one MRAM cell; depositing a mask layer conformally covering the second interlayer dielectric; perform a planarization process to remove the mask layer in the memory region; after the step of performing the planarization process, removing the mask layer in the logic region.