Semiconductor structure and method for forming the same

A method for forming a semiconductor structure, comprising:

• providing a semiconductor substrate, wherein an isolation structure, an active region and a buried word line structure are formed on the semiconductor substrate, and a first dielectric layer is formed on a top surface of the buried word line structure;
• determining a position of a bit line contact opening on a top surface of the semiconductor substrate and a top surface of the first dielectric layer, wherein the bit line contact opening at least exposes a part of the active region, and the bit line contact opening at least further exposes a part of the first dielectric layer or a part of the isolation structure;
• etching the active region, the first dielectric layer and the isolation structure exposed by the bit line contact opening according to the position of the bit line contact opening until the active region is etched to a preset depth to form a bit line contact window;
• and
• forming a second dielectric layer on a surface of the isolation structure and a surface of the first dielectric layer that are positioned at a depth greater than a depth at which a surface of the active region in the bit line contact window is positioned;
• wherein a top surface of the second dielectric layer is flush with the surface of the active region in the bit line contact window and lower than the top surface of the semiconductor substrate, and a top of the second dielectric layer is wider than a bottom of the second dielectric layer.