A self-aligned contact method includes, firstly, forming a plurality of stack structures on a semiconductor substrate. The stack structures separate each other and each has a first polysilicon layer, an insulating layer on the first polysilicon layer and a second polysilicon layer on the insulating layer. Secondly, a spacer forms on the sidewall of the stack structures, and then a dielectric layer is formed on the stack structures, the spacers and the semiconductor substrate. Finally, the portion of the second polysilicon layer is used as a buffer for forming a contact window by removing a portion of the dielectric layer. The contact window is located between two stack structures.