Magnetoresistive random access memory devices include a first magnetic layer, a tunnel barrier layer formed on the first magnetic layer, and a second magnetic layer formed on the tunnel barrier layer. The tunnel barrier includes first regions having a first thickness and second regions having a second thickness that is greater than the first thickness. The tunnel barrier layer includes a first barrier layer formed from a first material and a second barrier layer formed from a second material different from the first material, the second layer being present only in the second regions.