Patent ID: 7170792

Claim:
A semiconductor device comprising: a main word line extending in a first direction; a common word line extending in a second direction across the first direction; a sub word driver coupled to the main word line and the common word line; and a sub word line extending in the first direction and coupled to the sub word driver; wherein the sub word driver outputs a first voltage, a second voltage, or a third voltage to the sub word line selectively according to a combination of a first signal on the main word line and a second signal on the common word line, wherein the first, second, and third voltage are different voltage; wherein the sub word driver includes a first MOS transistor having a source and a drain which are coupled between the sub word line and a first node supplied the first voltage, a second MOS transistor having a source and a drain which are coupled between the sub word line and a second node supplied the second voltage, and a third MOS transistor having a source and a drain which are coupled between the sub word line and a third node supplied the third voltage; wherein the first node is coupled to the common word line, and wherein the second signal varies between the first voltage and a fourth voltage.