A low parasitic capacitance Schottky diode including a lightly doped polycrystalline silicon island that is formed on a shallow trench isolation (STI) pad such that the polycrystalline silicon island is entirely isolated from an underlying silicon substrate by the STI pad. The resulting structure reduces leakage and capacitive coupling to the substrate. Silicide contact structures are attached to lightly-doped and heavily-doped regions of the polycrystalline silicon island to form the Schottky junction and Ohmic contact, respectively, and are connected by metal structures to other components formed on the silicon substrate. The STI pad, polycrystalline silicon island, and silicide/metal contacts are formed using a standard CMOS process flow to minimize cost. A bolometer detector is provided by measuring current through the diode in reverse bias. An array of such detectors comprises an infrared or optical image sensor.