Please refer following steps for M.2 RAID function.
1. Load BIOS Optimal default by press F3 2. Change submenu to SATA And RST Configuration (under Advanced menu) 3. Change SATA Mode Selection to Intel RST Premium with Intel Optane System Acceleration 4. Change both of PCIE M.2-M2 and PCIE M.2-M1 to RST Controlled 5. Press F4 to save & exit BIOS menu 6. After reboot the system, please enter BIOS menu then can create RAID by Intel Rapid Storage Technology which under Advanced menu also.