A semiconductor device includes a one-time programmable (OTP) memory including a key program area and a plurality of key protection setting areas. A key is stored in the key program area, and a plurality of setting values that protect the key stored in the key program area are programmed in the key protection setting areas. The semiconductor device further includes a key register and a key protection control logic circuit. The key register is configured to load the key stored in the OTP memory. The key is accessible to secure software when the key is loaded into the key register. The key protection control logic circuit is configured to load the key stored in the OTP memory into the key register based on the setting values programmed in the key protection setting areas of the OTP memory.