Semiconductor structure and method for forming the same, and memory and method for forming the same

The present invention relates to a semiconductor structure and a method for forming the same, and a memory and a method for forming the same. The method for forming the semiconductor structure includes: providing a substrate on which a sacrificial layer and an active layer located on the sacrificial layer are formed; patterning the active layer to form several discrete active pillars; removing the sacrificial layer to form a gap; forming a bit line within the gap; and forming a semiconductor pillar on the top of the active pillar. The above method can reduce the planar size of the transistor and increase the storage density of the memory.