Devices and methods for controlling wafer uniformity using a gas baffle plate are disclosed. In one example, a device for plasma-based processes is disclosed. The device includes: a housing defining a process chamber and a baffle plate arranged above a wafer in the process chamber. The baffle plate is configured to control plasma distribution on the wafer. The baffle plate has a shape of an annulus that comprises a first annulus sector and a second annulus sector. The first annulus sector has a first inner radius. The second annulus sector has a second inner radius that is different from the first inner radius.