The present application relates to a semiconductor structure and its forming method. The semiconductor structure comprises a substrate; a first transistor, including a first channel region disposed within the substrate, and a first end disposed at surface of the substrate, the first end being adapted to connect with a first-type storage cell; and a second transistor, including a second channel region disposed within the substrate, and a second end disposed at surface of the substrate, the second end being adapted to connect with a second-type storage cell, the first channel region and the second channel region having different areas.