A manufacturing method for double-side capacitor of stack DRAM has steps of: forming a sacrificial structure in the isolating trench and the capacitor trenches; forming a first covering layer and a second covering layer on the sacrificial structure; modifying a part of the second covering layer; removing the un-modified second covering layer and the first covering layer to expose the sacrificial structure; removing the exposed part of the sacrificial structure to expose the electrode layer; removing the exposed electrode layer to expose the oxide layer; and removing the oxide layer and sacrificial structure to form the double-side capacitors.