Patent ID: 6882215

Claim:
A substrate bias generator of a semiconductor memory device having a voltage pump circuit to boost a substrate voltage in response to an input of an oscillating signal generated in an oscillator, said substrate bias generator further comprising: a substrate voltage level detector having said substrate voltage input thereto and outputting a signal which drives said oscillator in response to a substrate voltage level detected by said substrate voltage level detector; and a controller having input thereto a chip active enable signal, a self refresh mode enable signal, and an output signal of said substrate voltage level detector, a self refresh mode of said semiconductor memory device having an active state and a standby state being defined by said chip active enable signal and said self refresh mode enable signal, said controller controlling a switching operation of said substrate voltage level detector in response to said substrate voltage level detected by said substrate voltage level detector, said controller also controlling said switching operation of said substrate voltage level detector in response to said chip active enable signal and said self refresh mode enable signal such that said substrate voltage level detector is not operative to drive said oscillator in said stand-by state of said self-refresh mode only when the detected substrate voltage level is a desired level.