The study aims to investigate enhanced hot-carrier-induced degradation of MOSFETs due to moisture diffusion from inter-metal oxides. By studying different split of back-end in details, it is confirmed the impact of hot-carrier-induced degradation due to moisture diffusion under different conditions. Analyzing how much current drops after 10K times of programming and erasing verifies the cause of device degradation. Experimental results indicate that HDP thickness reduction, alloy after HDP, deposition of SRO layer before HDP and material of TEOS can efficiently enhance hot-carrier-induced degradation. According to the experimental results, the influence of moisture diffusion has been clarified, providing directions for enhancing the hot-carrier-induced degradation of MOSFETs, and providing relevant experience for subsequent product development.