Patent ID: 7825447

Claim:
A MOS capacitor comprising: first and second electrodes; an insulating film; and a semiconductor film including first and second channel formation regions and first, second, and third impurity regions, wherein the first impurity region has N-type conductivity; wherein the second and third impurity regions have P-type conductivity; wherein the first channel formation region is interposed between the first impurity region and the second impurity region; wherein the first channel formation region is in contact with the first impurity region and the second impurity region; wherein the first channel formation region overlaps the first electrode with the insulating film interposed therebetween; wherein the second channel formation region is interposed between the first impurity region and the third impurity region; wherein the second channel formation region is in contact with the first impurity region and the third impurity region; and wherein the second channel formation region overlaps the second electrode with the insulating film interposed therebetween.