Memory structure and its formation method

A method for forming a memory structure, the method comprising:

• providing a semiconductor substrate, wherein discrete active areas are arranged in rows and columns on the semiconductor substrate, and a first groove exists between two of the discrete active areas that are adjacent, the first groove being filled with an insulating layer;
• etching the discrete active areas and forming two second grooves along a row direction in each of the discrete active areas, wherein the two second grooves divide each of the discrete active areas into a drain located in middle of each of the discrete active areas and two sources located on both sides of the drain;
• etching to remove part of the insulating layer on both sides of a bottom of the second groove, and forming a third groove in the insulating layer to expose at least part of a surface of sidewalls on both sides of the active area at the bottom of the second groove, wherein the third groove is in connection with the second groove and the third groove is not connected in the row direction with another third groove;
• and
• forming a gate structure in the second groove and the third groove.