AlN ceramic substrate and heater for semiconductor manufacturing apparatus

A heater for a semiconductor manufacturing apparatus comprising an aluminum nitride ceramic substrate including yttrium aluminate, wherein the aluminum nitride ceramic substrate has a volume resistivity of 3×109 Ωcm or more at 550° C., and

• a resistance heating element embedded in the aluminum nitride ceramic substrate, wherein:
• the resistance heating element is formed of molybdenum, and
• in the aluminum nitride ceramic substrate, a first annular layer that is in contact with and surrounds the resistance heating element, and a second annular layer that surrounds the first annular layer are present, and the first annular layer has a higher yttrium content and a larger layer width than the second annular layer.