Low cost, easily integrable photodetectors (PDs) for silicon (Si) photonics are still a bottleneck for photonic integrated circuits (PICs), especially for wavelengths above 1.8 μm. Multilayered platinum diselenide (PtSe₂) is a semi-metallic two-dimensional (2D) material that can be synthesized below 450°C. We integrate PtSe₂ based PDs directly by conformal growth on Si waveguides. The PDs operate at 1550 nm wavelength with a maximum responsivity of 11 mA/W and response times below 8.4 μs. Fourier transform infrared spectroscopy (FTIR) in the wavelength range from 1.25 μm to 28 μm indicates the suitability of PtSe₂ for PDs far into the infrared wavelength range. Our PtSe₂ PDs integrated by direct growth outperform PtSe₂ PDs manufactured by standard 2D layer transfer. The combination of IR responsivity, chemical stability, selective and conformal growth at low temperatures, and the potential for high carrier mobility, make PtSe₂ an attractive 2D material for optoelectronics and PICs.