The invention provides a method for making a flash memory. The method comprises the following steps: forming a tunneling oxidation layer, a floating grid, an inter-grid medium layer and a control grid in turn on a semiconductor substrate; forming side walls on the two sides of the control grid and the floating grid; forming a source/drain in the semiconductor substrate on the two sides of the control grid and the floating grid; forming a silicide layer on the semiconductor substrate, wherein the silicide layer covers the control grid and the floating grid; etching the silicide layer by a dry etching method and defining a silicide blocking area; forming an inter-layer medium layer in a non-silicide blocking area, wherein a contact hole exposing out of the source/drain and the control grid is formed in the inter-layer medium layer; forming a diffusion blocking layer on the inner wall of the contact hole and filling conductive substances in the contact hole to form a conductive plug; and performing metal wiring to form the flash memory. The invention prevents cavity in the conductive substances filled in the contact hole and improves the electrical performance of the semiconductor device.