The present invention relates to a solid electrolyte capacitor having a small size, a high capacitance, a low ESR and an excellent LC value, which includes a jacketed capacitor element obtained by sequentially stacking a dielectric oxide film layer, a semiconductor layer and an electrically conducting layer on a surface of a valve-acting metal sintered body or electrically conducting oxide sintered body connected with an anode lead, wherein the thickness of the semiconductor layer in the vicinity of the anode lead-connection point on the sintered body face connected with an anode lead is 5 .mu.m or less, and also relates to an electronic circuit and electronic device using the capacitor.