A power device with trenched gate structure, includes: a substrate having a first face and a second face opposing to the first face, a body region of a first conductivity type disposed in the substrate, a base region of a second conductivity type disposed in the body region, a cathode region of the first conductivity type disposed in the base region, an anode region of the second conductivity type disposed in the substrate at the second face a trench disposed in the substrate and extending from the first face into the body region, and the cathode region encompassing the trench, wherein the trench has a wavelike sidewall, a gate structure disposed in the trench and an accumulation region disposed in the body region and along the wavelike sidewall. The wavelike sidewall can increase the base current of the bipolar transistor and increase the performance of the IGBT.