Patent ID: 7188267

Claim:
A semiconductor device formed on a semiconductor substrate, comprising: a cell array disposed on the semiconductor substrate, configured to operate synchronously with a first clock signal, and configured to output a first output signal delayed by a first delay time from the first clock signal; a first measuring circuit configured to measure indirectly a first increase and a first decrease of the first delay time, the first measuring circuit comprising: a first oscillation circuit disposed on the semiconductor substrate and configured to oscillate for a first constant time, a first counter configured to count a first oscillation frequency during the first constant time, a first value-detecting circuit configured to determine a second increase which is configured to signify the first decrease of the first oscillation frequency and a second decrease which is configured to signify the first increase of the first oscillation frequency; a setting circuit configured to operate synchronously with the first clock signal, configured to output a second clock signal delayed from the first clock signal by a second delay time adding the first increase and subtracting the first decrease; and a second circuit configured to input the first output signal and configured to operate synchronously with the second clock signal.