Formation method of semiconductor device

The invention provides a formation method of a semiconductor device. After a grid medium layer is formed on a semiconductor substrate, a first material layer, a barrier layer and a second material layer are sequentially formed on the grid medium layer from bottom to top, and the second material layer, the barrier layer, the first material layer and the grid medium layer are etched to form a fake-grid stack. In the above technical scheme, the grid medium layer comprises three layers of fake-grid materials in the fake grid, in the process of removing the fake-grid structure of the three layers of materials, the barrier layer can be used as an etching finish point for effectively removing the second material layer by a dry etching method, and after the barrier layer is removed, the first material layer reserved is removed by a wet etching process having high etching ratio relative to the first material layer and the grid medium layer, and the tri-layer fake-grid materials can be completely removed, and the grid medium layer below the tri-layer fake-grid materials can be protected from damage.