An apparatus for depositing a thin layer and associated method, the apparatus including a process chamber; a support in the process chamber, substrates being supportable on the support at different heights; a gas injector configured to inject a gas into the process chamber; and a heater configured to heat the process chamber, wherein the gas injector includes a first injector configured to inject a first gas; and a second injector configured to inject a second gas, a flow rate of the first gas injected from the first injector ranges from 120 sccm to 240 sccm, and a flow rate of the second gas injected from the second injector ranges from 1,200 sccm to 2,400 sccm.