Multilayer reflective film coated substrate, manufacturing method thereof, reflective mask blank, and reflective mask

A multilayer reflective film coated substrate, comprising:

• a multilayer under film, which consists of a first plurality of first Mo/Si alternately-layered films and is formed on a substrate, the first plurality of first Mo/Si alternately-layered films being formed by alternately laminating a first combination of an Si layer and a Mo layer as one cycle so that a cycle length of the multilayer under film is given as d bottom (unit:nm), and
• a multilayer reflective film, which consists of a second plurality of second Mo/Si alternately-layered films for reflecting exposure light and is formed on the multilayer under film, the second plurality of second Mo/Si alternately-layered films being formed by alternately laminating a second combination of an Si layer and a Mo layer as one cycle so that a cycle length of the multilayer reflective film is given as d top (unit:nm), the cycle length of each said second plurality of second Mo/Si alternately-layered films being substantially the same,
• wherein d bottom>d top, and
• a relationship of a formula (1) is satisfied when d bottom>d top, the formula (1) being given by
• (n+0.15)×d top≦d bottom≦(n+0.9)×d top
• where n is a natural number equal to or greater than 1.