Particle traps for semiconductor wafer vapor processors and methods of filtering particles in a semiconductor wafer processor are described. In accordance with a preferred implementation, a semiconductor wafer processor includes a processing chamber for containing a gas during processing of a semiconductor wafer. A particle trap is positioned within the reaction chamber and is operative for removing particles within the processing chamber. In one version, the particle trap is an electrostatic precipitator charged for removing particles from the gas. In accordance with another implementation, a semiconductor wafer vapor processor includes a processing chamber for containing a gas during processing of a semiconductor wafer. A wafer holder is provided within the processing chamber. A particle trap comprising at least two chargeable elements is positioned within the processing chamber and is spaced from the wafer holder. In one version, the processing chamber is a reaction chamber. In another version, the processing chamber is a vacuum chamber. In accordance with yet another aspect, a method of filtering particles in a semiconductor wafer processor includes: causing processing gases to flow through a processing chamber of a semiconductor wafer processor; filtering particles from within a processing reactor of the processing chamber.