Methods for forming semiconductor structures are provided. The method for forming the semiconductor structure includes forming a control gate over a substrate and forming a dielectric layer covering the control gate. The method further includes forming a conductive layer having a first portion and a second portion over the dielectric layer. In addition, the first portion of the conductive layer is separated from the control gate by the dielectric layer. The method further includes forming an oxide layer on a top surface of the first portion of the conductive layer and removing the second portion of the conductive layer to form a memory gate.