PURPOSE: To improve the electrostatic breakdown strength of an electrostatic breakdown preventive circuit by a method wherein the protective resistance element of the electrostatic breakdown preventive circuit is constituted of a high-melting point metal film.
CONSTITUTION: A protective resistance element of an electrostatic breakdown preventive circuit is constituted of a first protective resistance element R1 and a second protective resistance element R2. The element R1 is formed of the same conductive layer 13 as that constituting a gate electrode 13 of a MISFET for transfer use of a memory cell. The element R2 is formed of the same conductive layer 29 as that constituting respectively a main word line 29 and a subword line 29, which are extendedly provided to the upper part of the memory cell. This layer 29 is formed of a high-melting point metal film, its melting point is high compared to a polycrystalline silicon layer, its current density is small and its specific resistance value is smaller by at least one digit or more. By this constitution, as the generation of heat due to a surge current, which is made to flow through the protective resistance element, can be reduced, a thermal breakdown of this protective resistance element is prevented and an electrostatic breakdown of the electrostatic breakdown preventive circuit can be prevented.
NAKAMURA HIDEAKI
HONJO SHIGERU
YOSHIZAKI KAZUO
YAMAZAKI YASUSHI
HITACHI VLSI ENG