FinFET, a quasi-planar device has gained tremendous importance in the semiconductor industry because it has the ability to suppress all the short-channel effects. The silicon fin of FinFET can be of different shapes-rectangular, trapezoidal, triangular, convex, concave etc. In this paper, we have discussed subthreshold swing, threshold voltage of different fin structures and drain current based on angle of inclination, fin width and applied gate voltages. We also include change of channel capacitance of triangular fin based on different fin width. Some novel analytical formula expression for subthreshold swing has been discussed. In MATLAB, we have plotted the variation of different graphs based on different parameters of FinFETs and obtain their respective results to prove that our dimensions are superior to other values.