Methods of forming the MRAM generally include forming an array of MTJ having sub-lithographic dimensions. The array can be formed by providing a substrate including a MTJ material stack including a reference ferromagnetic layer, a tunnel barrier layer, and a free ferromagnetic layer on an opposite side of the tunnel barrier layer. A hardmask layer is deposited onto the MTJ material stack. A first sidewall spacer is formed on the hardmask layer in a first direction. A second sidewall spacer is formed over the first sidewall in a second direction, wherein the first direction is orthogonal to the second direction. The second sidewall spacer intersects the first sidewall spacer. The first sidewall spacer is processed using the second sidewall spacer as mask to form a pattern of oxide pillars having sub-lithographic dimensions. The pattern of oxide pillars are transferred into the MTJ stack to form the array.