Provided are a system and a method for treating a substrate. The substrate treating system may include a process chamber including a body with an open top and a dielectric window hermetically sealing the top of the body from an outside, a supporting unit provided in the process chamber to support a substrate, a gas-supplying unit supplying a process gas into the process chamber, a plasma source provided outside the process chamber to generate plasma from the process gas supplied into the process chamber, and a heating unit heating the dielectric window. The heating unit may include a heater and a thermally conductive layer provided on one of surfaces of the dielectric window.