In this work, we presented for the first time a miniaturized 3D printed, in-plane, and gatecontrolled electrochemical capacitor-diode (G-CAPode). This novel device consists of a working capacitor with ion-sieving characteristics (CAPode) which is controlled by a third "gate" electrode to simultaneously realize both, diodeand transistor-like behavior simultaneously. By applying a Ubias between the gate electrode and the counter electrode of the working capacitor (W-Cap), the entire potential range, i.e. the operational window, of the W-Cap can be positioned either in the positive (high capacitance, "on") or negative voltage (low capacitance, "off") potential range. These switching characteristics result in a tunable capacitance of the W-Cap. In the "off" state (positive gate Ubias), the blocking direction of the CAPode (redundant to the W-Cap) dominates exhibiting low capacitance, whereas in the "on" state (negative gate Ubias) the open polarization direction of the CAPode prevails, leading to a high capacitance.