Solid electrolytic capacitor element, solid electrolytic capacitor, and method for manufacturing solid electrolytic capacitor element

A method of producing a solid electrolytic capacitor element, the method comprising:

• forming a dielectric layer on at least a first main face of an anode comprising a valve acting metal substrate and having a front end face and a base end face;
• forming a mask layer comprising an insulating material on the dielectric layer adjacent the base end face;
• immersing the anode with the mask layer on the dielectric layer from the front end face side in a solid electrolyte-containing treatment liquid until the treatment liquid contacts the mask layer;
• and
• pulling up the anode from the treatment liquid and drying the treatment liquid, wherein the drying is performed while the anode is inverted upside down from a state in the immersion so as to form a protrusion in the solid electrolyte layer adjacent the mask layer such that a largest thickness of the solid electrolyte layer at the protrusion is larger than a thickness of the solid electrolyte layer at a rest of the solid electrolyte layer excluding the protrusion.