An isolation method for a single crystalline silicon microstructure using a triple layer structure is disclosed. The method includes forming the triple layer composed of an insulation layer formed over an exposed surface of the silicon microstructure, a conductive layer formed over the entire insulation layer, and a metal layer formed over a top portion of the microstructure; and partially etching the conductive layer to form electrical isolation between parts of the microstructure. The method does not require a separate photolithography process for isolation, and can be effectively applied to microstructures having high aspect ratios and narrow trenches. Also disclosed are single crystalline silicon microstructures having a triple layer isolation structure formed using the disclosed method.