An improved upper electrode system has a multi-part electrode in which a central portion of the electrode having high wear is replaceable independent of an outer peripheral portion of the electrode. The upper electrode can be used in plasma processing systems for processing semiconductor substrates, such as by etching or CVD. The multi-part upper electrode system is particularly useful for large size wafer processing chambers, such as 300 mm wafer processing chambers for which monolithic electrodes are unavailable or costly.