A power multiplier system for an amplifier comprises a power multiplier control stage, an amplifier stage and a first switching stage connectable to the power multiplier control stage. The trench may be filled with a dielectric material or may have a conductive material in a central portion with a dielectric layer lining the walls of the trench. The concentration of the cationic impurity falls within a range of 1\xd710\u22127 to 6\xd710\u22126 equivalentL at the outlet port section. At least the shoulder portion, the body portion and the bottom portion include an inner layer, an intermediate layer and an outer layer.