A memory structure including a substrate, a memory cell, and a transistor is provided. The substrate includes a memory cell region and a peripheral circuit region. The memory cell is located in the memory cell region. The transistor is located in the peripheral circuit region. The transistor includes a gate, a first doped region, a second doped region, a first nickel silicide layer, and a second nickel silicide layer. The gate is located on the substrate and is insulated from the substrate. The first doped region and the second doped region are located in the substrate on two sides of the gate. The first nickel silicide layer is located on an entire top surface of the first doped region, and the second nickel silicide layer is located on an entire top surface of the second doped region.