A method of forming a semiconductor structure is provided. The method includes providing a substrate and forming a mask layer on the substrate, Next, dielectric isolations are formed in the mask layer and the substrate, wherein the dielectric isolations extend above the substrate. Then, the mask layer is removed to expose a portion of the substrate, and a dielectric layer is formed on the exposed portion of the substrate. Subsequently, a first conductive layer is formed on the dielectric layer, and a portion of the dielectric isolation is removed, wherein a top surface of the remaining dielectric isolation is lower than a top surface of the first conductive layer. Moreover, a conformal layer is formed over the substrate, and a second conductive layer is formed on the conformal layer.