Integrated particulate matter sensor with cavity

A particulate matter (PM) sensor comprises a substrate forming a cavity (5), the substrate comprising a semiconductor chip (4), and a light source (1) arranged in the cavity (5). The light source (1) is adapted to emit a light beam (7). The light beam (7) forms a detection volume (8) for particulate matter (9) outside the cavity (5). Optionally, the particulate matter sensor comprises an optical element (2) delimiting the cavity (5) at one end. The optical element (2) is configured to shape the light beam (7). Further, the particulate matter sensor comprises at least one photodetector (3) that is integrated into a surface of the semiconductor chip (4). The surface into which the at least one photodetector (3) is integrated faces the detection volume (8). The at least one photodetector (3) is adapted to detect light (10) scattered by particulate matter (9) in the detection volume (8).