MANUFACTURE OF SEMICONDUCTOR DEVICE

PURPOSE: To remove defects of voids due to BPSG use for improving the reliability of a semiconductor device by forming a buffer layer between a conductive layer and BPSG film and treating the surface of the conductive layer, when forming the high-conc. P BPSG film for a low-temp. planarizing process. CONSTITUTION: After forming a BPSG film 2 on the top of a semiconductor substrate 1, an impurity-contg. polysilicon 3 and tungsten silicide 4 are deposited and patterned to form bit lines 12. A buffer layer 5 is formed, BPSG film 6 is formed thereon by heat treatment, and BPSG film 7 is formed. Because of the buffer layer 5 between the conductive layer 12 and BPSG film 6, the buffer layer 5 absorbs excessive P from the BPSG film 6 during heat treating and diffuses into the buffer layer 5 to reduce the P concn. This prevents formation of voids due to use of high-concn. BPSG and hence improves the reliability of the semiconductor device.