| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor device using an oxide semiconductor evaluated by an evaluation method of calculating a carrier concentration of the oxide semiconductor around an ambient temperature.SOLUTION: In a transistor having an oxide semiconductor and a threshold voltage larger than 0 V, three and more carrier concentrations of the oxide semiconductor at measurement temperatures of 493 K and over and at measurement temperatures different from each other are measured, and correlation between the measured carrier concentrations and reciprocals of the measurement temperatures are plotted by using he measured carrier concentrations as single logarithms, and when the plotted dots are connected, a straight line is formed, and by extrapolation from the plotted each dot by a least-square method, a carrier concentration of the oxide semiconductor at the measurement temperature less than 493 K is calculated by using formula (1). Note that, in the formula, N(T) denotes a carrier concentration [piece/cm] at an absolute temperature, Edenotes an energy difference [eV] between a lower limit of a conduction band of the oxide semiconductor and a donor level, k denotes a Boltzmann constant and T denotes an absolute temperature [K].SELECTED DRAWING: Figure 1 |
