Filter membrane

A filter membrane, comprising:

• a membrane having a plurality of through holes configured to selectively separate a specific material from other materials in a processing medium, the membrane comprising a first layer, a second layer and a third layer formed such that the first layer has a first surface configured to be supplied with the processing medium, the third layer has a second surface on an opposite side with respect to the first surface of the first layer, and the second layer is formed between the first layer and the third layer,
• wherein the first layer includes a plurality of first convex portions and a plurality of first concave portions formed such that each of the first convex portions is formed from an interface between the second layer and the first layer toward the first surface of the first layer and has a cross-sectional area parallel to the first surface gradually decreasing toward the first surface of the layer, and that each of the first concave portions has a bottom at the interface between the second layer and the first layer, the third layer includes a plurality of second convex portions and a plurality of second concave portions formed such that each of the second convex portions is formed from an interface between the second layer and the third layer toward the second surface and has a cross-sectional area parallel to the second surface gradually decreasing toward the second surface, and that each of the second concave portions has a bottom at the interface between the second layer and the third layer and has a larger area than each of the first concave portions, the third layer is formed such that the second convex portions are formed to surround the second concave portions and connected to one another, the second layer has a plurality of through holes connecting the second concave portions and a first set of the first concave portions, and the first concave portions includes a second set of the first concave portions formed in regions opposing the second convex portions such that the second set of the first concave portions in each of the regions is connected to each other.