A new technique for laser trimming of polysilicon resistors has been developed. In this scheme an undoned poiysilicon film is at first patterned lithographically. The photoresist pattern is then used to prevent doping certain narrow areas of each resistor during the impurity implanting, thus the protected areas remain insulating after wafer processing.The subscqent laser scanning of the undoped regions can precisely reduce the resistance value by the lateral diffusion of impurities. Trimming can be accomplished by changing the laser power or position. A Q-switched Nd:YAG laser with its fundamental (1.06 μm) and second harmonic (0.53 μm) radiations was used successfully. The processing is applied to passivated resistors with negligible (approximately zero) post trimming drift and the TCRs of trimmed resistors can be matched to the ones of untrimmed resistors in the same film.