A wafer-supporting device for supporting a wafer thereon adapted to be installed in a semiconductor-processing apparatus includes: a base surface; and protrusions protruding from the base surface and having rounded tips for supporting a wafer thereon. The rounded tips are such that a reverse side of a wafer is supported entirely by the rounded tips by point contact. The protrusions are disposed substantially uniformly on an area of the base surface over which a wafer is placed, wherein the number (N) and the height (H [μm]) of the protrusions as determined in use satisfy the following inequities per area for a 300-mm wafer: (−0.5N+40)≤H≤53;5≤N≤100.