nested layout

is it possible to make the file structure like follows:

- routes
  - (user)
    - layout.tsx
    - [username].tsx

- routes
  - (user)
    - layout.tsx
    - [username].tsx

obviously

layout.tsx

layout.tsx

isn't the proper naming convention, but just wondering if it's possible to achieve something like that. Currently I'm doing

- routes
  - (user)
    - [username].tsx
  - (user).tsx // this is the layout

- routes
  - (user)
    - [username].tsx
  - (user).tsx // this is the layout

but routes/ is gets pretty cluttered fast as I create route groups