Generalizable Face anti-spoofing (FAS) approaches have recently garnered considerable attention due to their robustness in unseen scenarios. Some recent methods incorporate vision-language models into FAS, leveraging their impressive pre-trained performance to improve the generalization. However, these methods only utilize coarse-grained or single-element prompts for fine-tuning FAS tasks, without fully exploring the potential of language supervision, leading to unsatisfactory generalization ability. To address these concerns, we propose a novel framework called TF-FAS, which aims to thoroughly explore and harness twofold-element fine-grained semantic guidance to enhance generalization. Specifically, the Content Element Decoupling Module (CEDM) is proposed to comprehensively explore the semantic elements related to content. It is subsequently employed to supervise the decoupling of categorical features from content-related features, thereby enhancing the generalization abilities. Moreover, recognizing the subtle differences within the data of each class in FAS, we present a Fine-Grained Categorical Element Module (FCEM) to explore fine-grained categorical element guidance, then adaptively integrate them to facilitate the distribution modeling for each class. Comprehensive experiments and analysis demonstrate the superiority of our method over state-of-the-art competitors.