Summary form only given. The effect of short and narrow channels on MOS transistor capacitance are discussed. To identify the short-channel effect, transistors with 100 mu m width and L//e //f //f of 7. 8 mu m, 3. 8 mu m, 1. 8 mu m, and 0. 8 mu m, were measured. Just above the threshold voltage, C//g //d decreases. This may be due to the shielding effect of the channel connected to source. The most significant short-channel effect is that the distinction between the saturation and linear region becomes vague. This agrees with the dc characteristics. As a result, C//g //d begins to increase in the saturation region. Narrow-channel devices with L = 100 mu m and several W//e //f //f from 9. 2 mu m to 1. 2 mu m were measured and normalized. Normalized C//g //s for the narrow device is larger because of the fringing portion along the field edge. In addition, the narrow C//g //s increases with V//g significantly. Presumably this is due to the inversion layer width increasing with gate voltage.