Structural effects, especially corner angle of upper-corners of trapezoidal and rectangular, and triangular cross-sectional shapes of silicon nanowire field-effect transistors on effective carrier mobility and normalized inversion charge density have been investigated. 〈1 0 0〉-directed silicon nanowire field-effect transistors with semi-gate around structure fabricated on (1 0 0)-oriented silicon-on-insulator wafers were evaluated. As the upper-corner angle decreased from obtuse to acute angle, we observed an increased amount of inversion charge using split-CV measurement. On the other hand, the effective carrier mobility dependence on the upper-corner angle seems to have an optimized point near 100° at 296 K. Although normalized inversion charge density was the largest with acute angles, effective carrier mobility with acute upper-corner angle was severely degraded. Considering the intrinsic delay time of SiNW FET, SiNW FETs with trapezoidal cross-section with upper-corner angle of 100° is more suitable in this work to achieve high electrical performance. We believe these findings could represent guidelines for the design of high-performance SiNW FETs.