A sensor (10) includes a cavity (31) formed by a substrate (11), an adhesive (21), and a filter (22). A sensing element (14) is located inside the cavity (31) while electrical contacts (17, 18) coupled to the sensing element (14) are located outside the cavity (31). The filter (22) protects the sensing element (14) from physical damage and contamination during die singulation and other assembly processes. The filter (22) also improves the chemical sensitivity, selectivity, response times, and refresh times of the sensing element (14).