The gross features of previous computer results on stable accumulation and depletion layers are explained analytically. Further, the drift velocity of the accumulation plane in the singular limit,D=0, is obtained by a simple geometric construction based solely on the velocity‐field characteristic. This result is related to the drift velocity of the finite accumulation layer, at the same outside velocity, for theD≠0 case via a stringent inequality. For the general case,D=D(F), a new integral equation is derived from the starting differential equations.