Retention device

A retention device comprising a retention substrate including:

• a plate-shaped member having a first surface and a second surface and containing a ceramic material as a main component, the first surface for retaining an object, the second surface disposed opposite to the first surface;
• a gas channel formed in the plate-shaped member;
• and a gas-permeable porous body filling part of the gas channel and containing a ceramic material as a main component,
• wherein the gas channel includes a vertical channel section and a horizontal channel section, the vertical channel section having a gas outlet that opens in the first surface and extending from the gas outlet toward the second surface, the horizontal channel section connected to the vertical channel section and extending parallel to the first surface, and
• wherein the porous body fills the vertical channel section such that a space is formed on a side of the porous body adjacent to the second surface and inside the horizontal channel section.