Methods are provided for fabricating an SOI component on a semiconductor layer/insulator/substrate structure including a diode region formed in the substrate. The method comprises, in accordance with one embodiment, forming a shallow trench isolation (STI) region extending through the semiconductor layer to the insulator. A layer of polycrystalline silicon is deposited overlying the STI and the semiconductor layer and is patterned to form a polycrystalline silicon mask comprising at least a first mask region and a second mask region. First and second openings are etched through the STI and the insulator using the mask as an etch mask. N- and P-type ions are implanted into the diode region through the openings to form the anode and cathode of the diode. The anode and cathode are closely spaced and precisely aligned to each other by the polycrystalline silicon mask. Electrical contacts are made to the anode and cathode.