BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross sectional view showing a prior art surface-mounting type capacitor; FIGS. 2A and 2B are a longitudinal cross sectional view of a surface-mounting type capacitor according to a first embodiment of this invention and a transversal cross sectional view along a line 2B-2B of FIG. 2A, respectively; FIGS. 3A and 3B are a longitudinal cross sectional vi