Nonvolatile storage device and process for production thereof

Provided is a nonvolatile storage device (10) which has a reduced initiation voltage and can have a low driving voltage. The nonvolatile storage device (10) comprises a semiconductor substrate (100), a first electrode layer (105) formed on the semiconductor substrate (100), an oxygen-deficient first tantalum oxide layer (106x) formed on the first electrode layer (105) and having a composition represented by TaOx (0.8 = x = 1.9), a second tantalum oxide layer (106y) formed on the first tantalum oxide layer (106x) and having a composition represented by TaOy (2.1 = y), and a second electrode layer (107) formed on the second tantalum oxide layer (106y), wherein the second tantalum oxide layer (106y) has a columnar structure composed of multiple columnar bodies.