The present invention provides a photo-mask for manufacturing structures on a semiconductor substrate, which comprises a photo-mask substrate, a first pattern, a second pattern and a forbidden pattern. A first active region, a second active region are defined on the photo-mask substrate, and a region other than the first active region and the second active region are defined as a forbidden region. The first pattern is disposed in the first active region and corresponds to a first structure on the semiconductor substrate. The second pattern is disposed in the second active region and corresponds to a second structure on the semiconductor substrate. The forbidden pattern is disposed in the forbidden region, wherein the forbidden pattern has a dimension beyond resolution capability of photolithography and is not used to form any corresponding structure on the semiconductor substrate. The present invention further provides a method of manufacturing semiconductor structures.