Network slicing is a key enabling technology for 5G/B5G networks, allowing diverse services with distinct requirements to coexist on shared infrastructure. However, ensuring the trustworthiness of slices and improving performance, reliability, and security remains a significant challenge. This paper proposes a Hierarchical Fuzzy Trust System (H-FTS) to evaluate the trustworthiness of network slices. The system integrates Quality of Service (QoS) metrics (Latency, PLR, Throughput), Slice Failure Rate (SFR), Security Posture (SP), and Isolation Integrity (II). A lower-level Type-1 Fuzzy Logic System (T1 FLS) assesses the QoS score. This score, along with SFR, SP and II, is fed into an upper-level Interval Type-2 FLS (IT2 FLS) to compute Slice Trust (ST) score. Simulation results demonstrate the effectiveness of H-FTS, indicating that improvements in QoS, SP, and II have a positive impact on ST, while SFR shows a negative influence. The proposed H-FTS offers an interpretable and structured approach to trust assessment, essential for managing complex network slicing ecosystems.