nd 1B, in which FIG. 6A is a cross-sectional view and FIG. 6B is a top view of the semiconductor device;FIG. 7 is a cross-sectional view illustrating a fifth modification to the first embodiment shown in FIGS. 1A and 1B;FIG. 8 is a cross-sectional view illustrating a sixth modification to the first embodiment shown in FIGS. 1A and 1B;FIGS. 9A through 9E are cross-sectional views illustrating the s